Observation 1) Until now despite many feature requests over the years, “Maximize On Play” for the 2nd monitor detached Game tab hasn’t been implemented.
Observation 2) Asset store packages and custom scripts were released that fixed and offered this functionality. All of these packages and scripts however are now deprecated as of version 2019.
Therefore, I was thinking of putting the time into learning UIElements if and only if in doing so I would be able to program my own implementation to allow this behaviour? I consider the ability to “Maximize On Play” on the 2nd monitor a requirement for my workflow. Therefore if I can kill 2 birds with one stone (learn the new UIElements whilst coding this desired behaviour) that would be great. So is this possible or would I instead need to learn the “soon to superseded” Editor GUI to do this? In which case I probably won’t since I don’t see the point in learning something from scratch that’s already being replaced by something newer.