--- a/browser/components/customizableui/content/panelUI.inc.xul
+++ b/browser/components/customizableui/content/panelUI.inc.xul
@@ -74,17 +74,16 @@
 #endif
 #endif
                          command="cmd_quitApplication"/>
         </hbox>
       </footer>
     </panelview>
 
     <panelview id="PanelUI-history" flex="1">
-      <label value="&appMenuHistory.label;" class="panel-subview-header"/>
       <vbox class="panel-subview-body">
         <toolbarbutton id="appMenuViewHistorySidebar"
                        label="&appMenuHistory.viewSidebar.label;"
                        type="checkbox"
                        class="subviewbutton subviewbutton-iconic"
                        key="key_gotoHistory"
                        oncommand="SidebarUI.toggle('viewHistorySidebar'); PanelUI.hide();">
           <observes element="viewHistorySidebar" attribute="checked"/>
@@ -125,17 +124,16 @@
                      oncommand="PlacesCommandHook.showPlacesOrganizer('History'); CustomizableUI.hidePanelForNode(this);"/>
     </panelview>
 
     <panelview id="appMenu-library-recentlyClosedTabs"/>
     <panelview id="appMenu-library-recentlyClosedWindows"/>
 
     <panelview id="PanelUI-remotetabs" flex="1" class="PanelUI-subView"
                descriptionheightworkaround="true">
-      <label value="&appMenuRemoteTabs.label;" class="panel-subview-header"/>
       <vbox class="panel-subview-body">
         <!-- this widget has 3 boxes in the body, but only 1 is ever visible -->
         <!-- When Sync is ready to sync -->
         <vbox id="PanelUI-remotetabs-main" observes="sync-syncnow-state">
           <vbox id="PanelUI-remotetabs-buttons">
             <toolbarbutton id="PanelUI-remotetabs-view-sidebar"
                            class="subviewbutton subviewbutton-iconic"
                            observes="viewTabsSidebar"
@@ -222,17 +220,16 @@
                            label="&appMenuRemoteTabs.signin.label;"
                            oncommand="gSync.openPrefs('synced-tabs');"/>
           </vbox>
         </hbox>
       </vbox>
     </panelview>
 
     <panelview id="PanelUI-bookmarks" flex="1" class="PanelUI-subView">
-      <label value="&bookmarksMenu.label;" class="panel-subview-header"/>
       <vbox class="panel-subview-body">
         <toolbarbutton id="panelMenuBookmarkThisPage"
                        class="subviewbutton subviewbutton-iconic"
                        observes="bookmarkThisPageBroadcaster"
                        command="Browser:AddBookmarkAs"
                        onclick="PanelUI.hide();"/>
         <toolbarbutton id="panelMenu_bookmarkingTools"
                        label="&bookmarkingTools.label;"
@@ -258,41 +255,31 @@
       <toolbarbutton id="panelMenu_showAllBookmarks"
                      label="&showAllBookmarks2.label;"
                      class="subviewbutton panel-subview-footer"
                      command="Browser:ShowAllBookmarks"
                      onclick="PanelUI.hide();"/>
     </panelview>
 
     <panelview id="PanelUI-feeds" flex="1" oncommand="FeedHandler.subscribeToFeed(null, event);">
-      <label value="&feedsMenu2.label;" class="panel-subview-header"/>
     </panelview>
 
     <panelview id="PanelUI-containers" flex="1">
-      <label value="&containersMenu.label;" class="panel-subview-header"/>
       <vbox id="PanelUI-containersItems"/>
     </panelview>
 
     <panelview id="PanelUI-helpView" flex="1" class="PanelUI-subView">
-      <label value="&helpMenu.label;" class="panel-subview-header"/>
       <vbox id="PanelUI-helpItems" class="panel-subview-body"/>
     </panelview>
 
     <panelview id="PanelUI-developer" flex="1">
-      <label value="&webDeveloperMenu.label;" class="panel-subview-header"/>
       <vbox id="PanelUI-developerItems" class="panel-subview-body"/>
     </panelview>
 
-    <panelview id="PanelUI-sidebar" flex="1">
-      <label value="&appMenuSidebars.label;" class="panel-subview-header"/>
-      <vbox id="PanelUI-sidebarItems" class="panel-subview-body"/>
-    </panelview>
-
     <panelview id="PanelUI-characterEncodingView" flex="1">
-      <label value="&charsetMenu2.label;" class="panel-subview-header"/>
       <vbox class="panel-subview-body">
         <vbox id="PanelUI-characterEncodingView-pinned"
               class="PanelUI-characterEncodingView-list"/>
         <toolbarseparator/>
         <vbox id="PanelUI-characterEncodingView-charsets"
               class="PanelUI-characterEncodingView-list"/>
         <toolbarseparator/>
         <vbox>

--- a/browser/components/customizableui/test/browser_981418-widget-onbeforecreated-handler.js
+++ b/browser/components/customizableui/test/browser_981418-widget-onbeforecreated-handler.js
@@ -12,20 +12,16 @@ add_task(async function testAddOnBeforeC
   let onBeforeCreatedCalled = false;
   let widgetSpec = {
     id: kWidgetId,
     type: "view",
     viewId: kWidgetId + "idontexistyet",
     onBeforeCreated(doc) {
       let view = doc.createElement("panelview");
       view.id = kWidgetId + "idontexistyet";
-      let label = doc.createElement("label");
-      label.setAttribute("value", "Hello world");
-      label.className = "panel-subview-header";
-      view.appendChild(label);
       document.getElementById("PanelUI-multiView").appendChild(view);
       onBeforeCreatedCalled = true;
     },
     onViewShowing() {
       viewShownDeferred.resolve();
     }
   };
 

--- a/browser/extensions/flyweb/bootstrap.js
+++ b/browser/extensions/flyweb/bootstrap.js
@@ -197,30 +197,25 @@ let FlyWebView = {
       tooltiptext: gFlyWebBundle.GetStringFromName("flyweb-button.tooltiptext"),
 
       onBeforeCreated(aDocument) {
         let panel = aDocument.createElement("panelview");
         panel.id = "flyweb-panel";
         panel.setAttribute("class", "PanelUI-subView");
         panel.setAttribute("flex", "1");
 
-        let label = aDocument.createElement("label");
-        label.setAttribute("class", "panel-subview-header");
-        label.setAttribute("value", gFlyWebBundle.GetStringFromName("flyweb-button.label"));
-
         let empty = aDocument.createElement("description");
         empty.id = "flyweb-items-empty";
         empty.setAttribute("mousethrough", "always");
         empty.textContent = gFlyWebBundle.GetStringFromName("flyweb-items-empty");
 
         let items = aDocument.createElement("vbox");
         items.id = "flyweb-items";
         items.setAttribute("class", "panel-subview-body");
 
-        panel.appendChild(label);
         panel.appendChild(empty);
         panel.appendChild(items);
 
         panel.addEventListener("command", this);
 
         aDocument.getElementById("PanelUI-multiView").appendChild(panel);
 
         this._sheetURI = Services.io.newURI("chrome://flyweb/skin/flyweb.css");

--- a/browser/locales/en-US/chrome/browser/browser.dtd
+++ b/browser/locales/en-US/chrome/browser/browser.dtd
@@ -157,17 +157,16 @@ These should match what Safari and other
 <!ENTITY closeWindow.accesskey "d">
 
 <!ENTITY bookmarksMenu.label "Bookmarks">
 <!ENTITY bookmarksMenu.accesskey "B">
 <!ENTITY bookmarkThisPageCmd.label "Bookmark This Page">
 <!ENTITY editThisBookmarkCmd.label "Edit This Bookmark">
 <!ENTITY bookmarkThisPageCmd.commandkey "d">
 
-<!ENTITY feedsMenu2.label "Subscribe to This Page">
 <!ENTITY subscribeToPageMenupopup.label "Subscribe to This Page">
 <!ENTITY subscribeToPageMenuitem.label "Subscribe to This Page…">
 <!ENTITY addCurPagesCmd.label "Bookmark All Tabs…">
 <!ENTITY showAllBookmarks2.label "Show All Bookmarks">
 <!ENTITY recentBookmarks.label "Recently Bookmarked">
 <!ENTITY otherBookmarksCmd.label "Other Bookmarks">
 <!ENTITY mobileBookmarksCmd.label "Mobile Bookmarks">
 <!ENTITY bookmarksToolbarChevron.tooltip "Show more bookmarks">
@@ -236,18 +235,16 @@ These should match what Safari and other
 <!ENTITY hideBookmarksSidebar.label         "Hide Bookmarks Sidebar">
 <!ENTITY viewBookmarksToolbar.label         "View Bookmarks Toolbar">
 <!ENTITY hideBookmarksToolbar.label         "Hide Bookmarks Toolbar">
 <!ENTITY searchBookmarks.label              "Search Bookmarks">
 <!ENTITY bookmarkingTools.label             "Bookmarking Tools">
 <!ENTITY addBookmarksMenu.label             "Add Bookmarks Menu to Toolbar">
 <!ENTITY removeBookmarksMenu.label          "Remove Bookmarks Menu from Toolbar">
 
-<!ENTITY containersMenu.label "Containers">
-
 <!-- LOCALIZATION NOTE (bookmarksSidebarGtkCmd.commandkey): This command
   -  key should not contain the letters A-F, since these are reserved
   -  shortcut keys on Linux. -->
 <!ENTITY bookmarksGtkCmd.commandkey "o">
 <!ENTITY bookmarksWinCmd.commandkey "i">
 
 <!ENTITY historyButton.label            "History">
 <!ENTITY historySidebarCmd.commandKey   "h">
@@ -335,17 +332,16 @@ These should match what Safari and other
 
 <!ENTITY showAllHistoryCmd2.label "Show All History">
 <!ENTITY showAllHistoryCmd.commandkey "H">
 
 <!ENTITY appMenuCustomize.label "Customize">
 <!ENTITY appMenuCustomize.tooltip "Customize the Menu and Toolbars">
 <!ENTITY appMenuCustomizeExit.label "Exit Customize">
 <!ENTITY appMenuCustomizeExit.tooltip "Finish Customizing">
-<!ENTITY appMenuHistory.label "History">
 <!ENTITY appMenuHistory.showAll.label "Show All History">
 <!ENTITY appMenuHistory.clearRecent.label "Clear Recent History…">
 <!ENTITY appMenuHistory.restoreSession.label "Restore Previous Session">
 <!ENTITY appMenuHistory.viewSidebar.label "View History Sidebar">
 <!ENTITY appMenuHistory.recentHistory.label "Recent History">
 <!ENTITY appMenuHelp.label "Help">
 <!ENTITY appMenuHelp.tooltip "Open Help Menu">
 
@@ -909,18 +905,16 @@ you can use these alternative items. Oth
      width of the plugin popup notification that can appear if a plugin has been
      blocked on a page. Should be wide enough to fit the pluginActivateNow.label
      and pluginActivateAlways.label strings above on a single line. This must be
      a CSS length value. -->
 <!ENTITY pluginNotification.width "28em">
 
 <!ENTITY uiTour.infoPanel.close "Close">
 
-<!ENTITY appMenuSidebars.label         "Sidebars">
-
 <!-- LOCALIZATION NOTE: (panicButton.view.mainTimeframeDesc, panicButton.view.5min, panicButton.view.2hr, panicButton.view.day):
      The .mainTimeframeDesc string combined with any of the 3 others is meant to form a complete sentence, e.g. "Forget the last: Five minutes".
      Please ensure that this remains the case in the translation. -->
 <!ENTITY panicButton.view.mainTimeframeDesc       "Forget the last:">
 <!ENTITY panicButton.view.5min                    "Five minutes">
 <!ENTITY panicButton.view.2hr                     "Two hours">
 <!ENTITY panicButton.view.day                     "24 hours">
 

--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -215,37 +215,22 @@ panelview {
   -moz-box-flex: 1;
 }
 
 #PanelUI-popup .panel-subview-body {
   margin: -4px;
   padding: 4px 4px;
 }
 
-.panel-subview-header,
 .subviewbutton.panel-subview-footer {
   box-sizing: border-box;
   min-height: 41px;
   padding: 11px 12px;
 }
 
-.panel-subview-header {
-  margin: -4px -4px 4px;
-  border-bottom: 1px solid var(--panel-separator-color);
-  color: GrayText;
-  font-variant: small-caps;
-  /* Workaround for min-height not being accounted for in vertical layout. */
-  height: 41px;
-}
-
-.cui-widget-panelview .panel-subview-header,
-photonpanelmultiview .panel-subview-header {
-  display: none;
-}
-
 .cui-widget-panelview .subviewbutton.panel-subview-footer {
   margin: 4px 0 0;
   -moz-box-pack: center;
 }
 
 #appMenu-popup > arrowscrollbox > autorepeatbutton,
 #PanelUI-popup > arrowscrollbox > autorepeatbutton {
   display: none;