about r10,10,32,32,transparent$fullscreen2,auto

fullscreen2 means that hide_fullscreen2.html would be used which you can modify as you like.

Yes, it must have been an older template file. The folder and template we had both dated from 15 May 2022. Our fix was hardcoding the absolute URL in place of {site}. And, thankfully, this feature of your plugin is working now with our modified (custom) buttons. 

Are there any other important differences in hide_fullscreen.html we should note? Will our hardcoded fix cause any problems with future updates? Let us know and we'll roll-back and/or integrate any changes you suggest.