Firefox-UI-Fix/src/utils/_native_menu.scss

@use "option" as *;

@mixin NativeMenu() {
  @include Option("widget.macos.native-context-menus", "widget.gtk.native-context-menus") {
    @content;
  }
}

@mixin NativeMenuPopup() {
  menupopup:is(#historyMenuPopup, #bookmarksMenuPopup),
  menupopup:not([placespopup="true"]) {
    @content;
  }
}

@mixin WinNativeMenu() {
  @media not (-moz-windows-non-native-menus) {
    @content;
  }
}

@mixin WinNonNativeMenu() {
  @media (-moz-windows-non-native-menus) {
    @content;
  }
}