Oooooooh…
Ok, I think we have a bug here.
The fix in XD 23, in particular, was related to the fact that position:fixed could go out-of-bounds of the plugin. Assuming no other positioned ancestor elements, elements that are fixed are positioned now based on the container (not the entire plugin panel)
Where it does fall apart is when the overall plugin height is larger than the container – fixed positioning doesn’t work there. So for now, I’d use fixed positioning only in the case of trying to adjust to the width and height of the panel for more complex layout. For example, you could have the top-level panel div have position: fixed; top: 0; left: 0; right: 0; bottom: 100px and then another div beneath it positioned at 100px from the bottom, and it’ll stay fixed to the size of the panel.