The double-click action on the window title bar is a Linux OS setting that works for all applications, so you need to check there. For me this is the Tweak Tool: right-click on the desktop -> Settings -> Windows -> Titlebar Actions.

The double-click action on the window title bar is a Linux OS setting that works for all applications, so you need to check there. For me this is the Tweak Tool: right-click on the desktop -> Settings -> Windows -> Titlebar Actions.

I've tried switching those settings around (even in dconf) but none of them worked; however, in doing so I realized the crux of the issue is that the entire firefox window excluding the actual webpage acts as the titlebar. So clicking and dragging anywhere in that area that isn't the webpage will move the entire window and thus, 'restore' it. AFAICT only firefox does this.

What OS? What Desktop? Think about it... there is nothing about Titlebar Actions in Firefox settings. see screenshot

Operating System: openSUSE Tumbleweed 20240716 KDE Plasma Version: 6.1.2 KDE Frameworks Version: 6.4.0 Qt Version: 6.7.2 Kernel Version: 6.9.9-1-default (64-bit) Graphics Platform: X11 Processors: 12 × Intel® Core™ i7-9850H CPU @ 2.60GHz Memory: 125.1 GiB of RAM Graphics Processor: Mesa Intel® UHD Graphics 630 Manufacturer: HP Product Name: HP ZBook 17 G6