Yes, a multi monitor set up. UHD 4K and 1080HD.
Editing is done on the 4K monitor.
When I open the Standalone version, still not able to resize the screen. It takes up the full screen.
Using Ctrl +1-3 only resizes (within the full size PI window) the view of the preview windows and not the PI main window at all.
The workaround for me has been to disconnect the 1080 monitor from the computer. Then I can resize the PI main window to what ever size I want and have the Min, Restore down, and Close options available.
If I resize PI to something smaller than full screen on the 4K monitor, exit PI, and restart it, it appears as I left it and now have those controls are on the upper right corner of the PI toolbar. I can now even drag PI to the 1080 monitor if I want.
This screenshot is what I see if I open PI full screen on the 4K monitor previously.