Personally, I would love to see Set flow to be implemented within the loop cut tool and have it mimic Swift Loop from 3ds Max. There are a few addons that provide a loop cut on mouse cursor, but none of them have Set flow (with a modal on/off) implemented.
E: It’s implemented in Fast Loop (a better Swift Loop for Blender).
Not working properly with 2.9. Repeat last action is not working with the tool. Also sometimes it doesn’t average the loops and you still have to do it manually in the option box. Pls for the love of all that is holy in blender update.