Hello!

I have noticed that there are many effects in two version, where one ends with (mask), e.g. there is an effect "Rotoscoping" and a "Rotoscoping (mask)". What is the difference?
I am running Kdenlive version: 21.12.3 on Windows 10.

I don't really understand the difference yet either, but here, at the info = ⓘ of the effect, is a first explanation:

This filter makes a snapshot of the frame before a keyframable vector based rotoscoping is applied. Use it together with the mask_apply effect, that uses a transition to composite the current frame's image over the snapshot. The typical use case is to add effects in the following sequence: this effect, zero or more effects, mask_apply. (mask_start)