WhiteSur-gtk-theme/src/sass/gtk/_applications-4.0.scss

//
// Extensions
//
window.background.csd {
  > stack, // GameMode setting
  > stack > scrolledwindow > viewport > box, // User Themes (Workspace) setting
  > box > stack > scrolledwindow > viewport > box {
    > list {
      @extend %circular_list;

      row.activatable { @extend %circular_row; }
    }
  }

  stack stack stack frame, // ArcMenu setting
  > stack > stack > box > frame, // Night Theme Switcher setting
  > stack > stack > box > box > frame, // Night Theme Switcher setting bottom lists
  > stack > box > stack > box > frame, // ArcMenu setting
  > stack > box > stack > scrolledwindow > viewport frame, // ArcMenu setting
  > stack > box > stack > box > scrolledwindow > viewport > frame, // ArcMenu setting
  > stack > grid > scrolledwindow > viewport > box > frame { // GSConnect setting
    > border { border: none; }

    > list {
      @extend %circular_list;

      row.activatable { @extend %circular_row; }
    }
  }

  > stack > box > box > list,
  > stack > box > stack > scrolledwindow > viewport > list { // ArcMenu setting sidebar
    border-bottom-left-radius: $wm_radius;
  }

  &.maximized, &.tiled, &.fullscreen {
    > stack > box > box > list,
    > stack > box > stack > scrolledwindow > viewport > list { // ArcMenu setting sidebar
      border-bottom-left-radius: $maximized_radius;
    }
  }
}