Unless I'm misunderstanding this completely it just sounds like you need to familiarise yourself with the different types of scenes that operate in Isadora.
Basically you can have 2 scenes operating simultaneously.
So for example you might have a scene which plays your video content on screen B, whilst simultaneously activating a background scene which shows video on screens A + C.
The benefit of this is that background scene will keep playing until it is deactivated. So it can play in the background of multiple scenes.
So in this scenario you could trigger a jump actor to go to the next scene where a different video plays on screen B. But the video on A +C would continue as if nothing has happened.
It's the same technique you would use to have an audio track which runs through multiple scenes.
This video explains it all