Now this has me stumped big time: Whenever I add the rotoscoping effect to a clip in the timeline the first keyframe is missing. I can add additional ones but not on the first frame of the clip. There is the plus sign but it is greyed out. Move to the next frame and I can click the plus sign for a keyframe.

Now what really bothers me is that until a few day ago this was no problem. I am on Windows 10 and have 20.08.1 and a nightly build installed. All versions exhibit the same behavior. I can load a project with rotoscoping no problem and there is a keyframe in the first frame of the clip. I have already uninstalled all kdenlive versions and installed them back again (in different folders) but the problem persists.

I will test this in my VM where I have Modicia installed that runs kdenlive 20.04.0. Any help or ideas are welcome.

Ok, my bad. It appears that a keyframe is only added once the area for rotoscoping has been defined. It doesn't matter on what frame one does that as a keyframe on the first frame is created anyway and on the frame where one created the area.
Sorry for sending ppl on a wild goose chase but I simply did not notice that before.