Agreed. I use the app on a Linux desktop PC. I dislike the Composer window being artificially constrained to only small or large size and firmly attached to the bottom edge of the window. I want to be able to resize my Composer window to my choosing and place it where I want (like any other window). Yes I know this is a personal preference, but why constrain this window, it spoils an otherwise pretty good app.

Correct, in small laptops it's a struggle to compose an email as the space is not enough. Having a full screen external window would be great.