Paint.net has a cool feature that I would like to see in Krita.
Assume you are using the brush tool and then use the color selection tool to pick a color. Paint.net has an option to automatically revert back to the brush tool after the color pick. No need to reselect the brush tool. A real time saver.

Use ctrl-click to pick a color when using the brush tool. Did you know we have an extensive manual at docs.krita.org?