Hi at all,
I have done a short Demo video (6m14s) with the description to show the use of that powerful feature.
In the demo you can see that I use four video source, but you can use more. I hope it can be useful.
File: Demo_MultiCameras-ExpertUsage_OpenMixers.(mov)
https://streamable.com/c40ia

@Andrea paz
I'm sorry if I don't write/answer to you (and others) in the Forum.

Thanks!
IgorBeg

PS:
If someone is interested to change the text in yellow colour, I can send the Cinelerra Project file with the screencast sources, without Music for license problems.