It avoids a lot of floating plugin windows (which is in line with the newer window management from C9 and onwards).
Here’s a video about tabbed plugin windows in Studio One:
As in SO, it should still be possible to pin a tabbed window to have more than one, if desired.
It would also be good if there would be an optional possibility to make the tabbed window follow track selection (and then have the plugins automatically exchanged to the new track selection). It could be a toggle button directly on the tabbed window. That would be better than a preference, since that choice could vary a lot depending on the situation.
Edit: and key commands to switch between tabs back and forth, to avoid using the mouse.