Does it have to be a “popup” exactly, or could you use a submenu style layout?
I replicated a bit of what Mendix has done with the profile picture at the top right of these pages for a “shopping cart”-like layout before, then edited the box to look like this style more
Did you ever find a solution for this problem Jason? I'm also looking to position my (modal) pop-up in the right bottom corner due to it being a chat window.
For all the css that I have tried, inline, !important, etc, I can't seem to overrule the Mendix inline styling with which the pop-up gets opened.