Tab key switches between 3D view and Preview
It may be common knowledge to everyone else, but I just found out and it is so much easier to switch between 3D view and Preview mode - just hit the Tab key 👍
Until now I have been using the mouse or the two key combinations Ctrl+5 and Ctrl+6 - but the Tab key is so more intuitive.
The Tab keyboard shortcut is not mentioned in the menu Help -> Keyboard Shortcuts - ? but I think it should be...