Some CSS tweaks aren't supported in 151.0-1 . . . ?

In my userChrome.css file, I have the following so I can have a "compact view" of bookmarks, menus, etc.:

:root{ --arrowpanel-menuitem-padding-block: 2px !important;}

The Sidebar still displays bookmarks, history, & synced tabs "compactly", but the items on the hamburger menu and in the folders on my bookmarks toolbar are given "Normal" (spacey) density. Any way I can fix this?