Absolute/relative position of FF UI urlbar

Add-ons Development
1

I’m a bit puzzled by some weird behavior I’ve encountered on Firefox 136 when using custom UI css rules (via userChrome.css).
This (making urlbar toggleable and in “overlay” mode) used to work just fine in FF 132:

toolbar#nav-bar
{
	top: -99px; 
    position: absolute;
	height: 0px!important;
	min-height: 0px!important;
}

toolbar#nav-bar:focus-within,
toolbar#nav-bar:hover,
toolbar#nav-bar:focus
{
	top: unset;
    position: absolute!important;
	height: unset!important;
	min-height: unset!important;
}

However, after updating to 136, I’ve noticed weird behavior I can’t comprehend - after focusing (via CTL+L) the urlbar to bring it on top and then clicking any of the extension icons - default CTRL+TAB to switch tabs simply stops working. At all. Period. The moment I remove position rule (i.e. it always stays relative) - everything works just fine.

 

I’m out of ideas myself so I’m curious if anyone else can figure this one out.