If you using a Mac, here are two ideas.
1. Assign a mouse key to cmd + = with
SteerMouse ($20). This makes it very easy to switch between the Mix and Edit windows.
30 day demo at:
http://plentycom.jp/en/steermouse/index.html
I use this all the time. I find it much faster than even using two monitors for Mix and Edit.
2.Use
SizeUp ($13) to "dock" the Mix and Edit windows.
Demo at:
http://www.irradiatedsoftware.com/sizeup/
Richard