Created attachment 168970 [details]
This is going to be headache without batch processing

Let's say I have 4-5 minutes of video and there are V1,V2,V3,V4,V5 tracks that are going in parallel these 5 minutes.

I want to make transition from V1 to V2, V2 to V3, etc... every 2 seconds. I want to cut (slice) those 5 tracks worth of 5 minutes (300 seconds) by cutting through all of them every 2 seconds and then deleting 2 seconds of clips that aren't supposed to be at A-roll (Main screen). Basically I am doing B-roll on steroids here. 

I don't want to make 150 !!! cuts and then 150 !!! transitions here, I want to be able to make it in batch (via script or something) since it is a simple action, but scaled to x150.

Also there are problem with transitions itself. Not only I have to apply 150 transitions, I need to make previous V1's 2 seconds to overlap next V2's 2 seconds 150 !!! times (and add this overlap to 2 seconds, to not shift all the timing). 

Also there are 2 scenarios of looping through those tracks: 
1) V1 - V2 - V3 - V4 - V5 - V4 - V3 - V2 - V1
2) V1 - V2 - V3 - V4 - V5 - V1 - V2 - V3 - V4 - V5

As far as I know compositions is not that friendly when applied to the clips from bottom to top (or vice versa, don't remember exactly, don't mind me).

So my proposal is:
1) Add batch processing to timeline. It must include: 
    a) From which time X to which time Y should the script work 
    b) Which tracks are affected by the script
    c) What action/s to apply in batch. Let's say I wan't to slice as in example and also add transitions to it which duration is Z milliseconds. 
2) Fix transitions (compositions) to work up and down correctly and intuitive (I want to be able to use not only fade in/fade out effects as it is simple and intuitive and works as intended, but also compositions)