I'd like to add a workflow idea that I think might be helpful. I'd like the designer toolbar to remember which element I had in focus, and which tab (style, navigator, interactions...nth) when a/b'ing changes between static and preview mode.
This would cut mouse clicks/movement in half and speed up workflow. Bonus if you can make the toolbar remember last scroll state as well.
Currently, the toolbar defaults to blank when exiting preview mode.