Thanks for your answer! I see, that's unfortunate.
These two things are why I prefer the legacy GUI:
I found it more manageable to have only those tabs opened that I needed in my every-day work process, which were just Pending Changes, Branch Explorer and Changesets. It always takes me a few seconds to find these among the side bar of the new GUI and I often click on the ones I don't need (like Branches, because I always mistake it for Branch Explorer). There isn't an option to hide the items I don't need. This makes the new GUI feel sluggish to me.
I don't need the comparison section of the Pending Changes view. It takes up half of the window, cluttering the screen with information that is not important to me. I didn't find an option to disable it. Yes, I can resize it to be almost hidden, but no, the resizing doesn't get saved, so I'd need to do that again every time I launch Plastic.