Automatic transition not available from 19.04
I don't know if this is a bug or just a change, but past year when placing a composite or a wipe effect on a video track (in a point where anotehr video tarck is overlapping the main one) the transition was correctly placed for the length of overlapping, this year, it just appear as a minimal lenght and it's necessary to adjust the length manually.
here a post about that: https://forum.kde.org/viewtopic.php?f=270&t=162588