Q
If you have not used the Q key up until now, you're welcome for the time you will soon save.
Switching between Timeline and source media window. Simple enough, but after you start using Q instead mousing between windows you will realize how many wasteful movements you have made until now.
Oh but remember not to hit Command + Q and end up quitting Resolve (at least if you don't have live save enabled that is).
Command + , and get those key commands flowing to your liking!