--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -1266,16 +1266,17 @@ toolbarpaletteitem[place="palette"] > #d
   padding-bottom: 10px;
 }
 
 #customization-panelHolder > #widget-overflow-fixed-list {
   flex: 0 1 auto; /* Size to content, but allow ourselves to shrink */
   display: flex;
   flex-direction: column;
   overflow-y: auto;
+  overflow-x: hidden;
 }
 
 #customization-container:not([photon]) #customization-panelHolder {
   overflow-y: hidden;
 }
 
 #customization-container[photon] #customization-panel-container {
   display: flex;

--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@@ -1213,16 +1213,20 @@ panelview:not([mainView]) .subviewbutton
 .subviewbutton.panel-subview-footer > .menu-accel-container {
   padding-inline-start: 6px;
 }
 
 .subviewbutton:not(.panel-subview-footer) {
   margin: 0;
 }
 
+%ifdef MOZ_PHOTON_THEME
+#widget-overflow-fixed-list .toolbarbutton-1 > .toolbarbutton-text,
+#widget-overflow-list .toolbarbutton-1 > .toolbarbutton-text,
+%endif
 .subviewbutton:not(.panel-subview-footer) > .toolbarbutton-text,
 /* Bookmark items need a more specific selector. */
 .PanelUI-subView .subviewbutton:not(.panel-subview-footer) > .menu-text,
 .PanelUI-subView .subviewbutton:not(.panel-subview-footer) > .menu-iconic-text {
   font: menu;
 }
 
 .subviewbutton[shortcut]::after {