The increased size of the bookmark toolbar menu (the one you can add as an icon that displays all of your bookmarks) is a common complaint about proton. I think we should use the unsupported compact mode to address this.

Suggested revision for same compactness as Firefox 78 ESR:

[uidensity=compact] menupopup > menuitem,
[uidensity=compact] menupopup > menu {
    padding-block: 2px;
}

Note: only tested on Windows.

In sum, all the menus I checked look okay with this change.

https://hg.mozilla.org/mozilla-central/rev/108a81c39b3d

I like this change, thanks!