I badly need 16:10, 1:1 and 2.11:1. Apart from aspect ratios Kdenlive offers everything for a professional 2D video editing; the little support for more aspect ratios is, in my opinion, the most severe defficiency of the program that makes it impossible to use it for professional production.

Thanks, looking forward to see any improvements.

Do you have examples of how and where you use these aspect ratios, why custom project profiles, crop and custom render profiles don't surfice and how not having these ratios stops it from being suitable, in your opinion for professional use whatever that term is supposed to mean.

Without examples the request and assertion is without proof.

You can make your own profiles with arbitrary aspect ratios etc. (and share them with the rest of the world, if you want).

Settings -> Manage profiles -> new profile (button with small green plus)

Maybe you should be able to start the profile manager from the "new profile"/"profile properties" dialogs.