Thanks for that, Silicon Pixel. I can get into the same state in Mac. You can usually dock any panel to a new location. That is, except this panel. It looks like a UI design issue. Please file the issue here.
I also see the "blank workspaces" panel. In this case, docking this specific panel to a new location fails to occur when dragging from the left edge of the Workspaces panel. Well, technically, the panel moves but without its functions. Once it's in this state, you can't drag it back to its original position to make Workspaces appear once more. A blank box (with two blue lines) appears (MacOS Sierra). It's now non-functional. Yeah, that's a little strange. Edit: I see now that the panel used to behave differently when you tried to collapse it in previous versions.
To reset your Workspaces panel to get back to the default layout, choose Workspace > Revert to Saved Layout. That should help you get back to square one. Edit: I see you found that temp solution. Thanks.
For now, I would recommend that you leave the Workspaces panel in its default position, and don't try to reposition it in any new custom 2 monitor layouts. It appears that placing it anywhere else but its default position might cause issues until we get this issue completely worked out.
I can see the designer's intention, however. To have your Workspaces panel open when you want it, closed when you don't need it. Edit: see Stefan's tip from June 14.
FYI, I noticed I can set a Keyboard Shortcut for the Workspaces panel, but it doesn't do anything. In my opinion, it should snap the panel open and closed. I'll point the UI folks to this thread, so I hope I can verify some of our observations and findings.
If you have time, please file your bug(s) to tell the designers how you would like the panel to behave and I'll look after that issue by putting a "watch" on the bug in our database.
Again, thank you for taking the time to point out this issue. Hopefully, this situation can be improved in future versions by filing our bugs and requests.
Kind Regards,
Kevin