Yesterday I saw the wonderfull screen transition effect of a samsung smartphone, where the fade out and fade in was not just all screen getting black and coming back, but the black color is arriving trough 2 lateral “tents” that arriving are making the screen black and the opposite. How to do it with shotcut? PS. the tents are blur and not just black blocks coming to blacking all the screen.
Not sure how to visualise your interpretation or explanation of what you saw, however - there are a number of transitions available in Shotcut for you to try. Have you gone through them yet?