tl;dr: Duplicate composites retain dependencies to their original assets and not duplicated ones. Why and how to stop them?
Because custom transitions require composites and take time to make, I'm trying to make up a library that I can reuse.
So, in a Folder in the Media Bin: Main composite that does the work, and then two other composites Clip A, Clip B to hold the assets. These will later have to contain other composites, because there is no easy way to cut out segments from the Editor timeline without 'promoting' them to composites and then dragging them in; but that's not a problem, and for placeholders they can also just be images.
So, as a test: a simple Opacity change from Clip A to Clip B works fine with a couple of images.
Then, I duplicate the whole Folder (Main, Plus clip A and B holders), call it Trans 2 and open up Clip A Composite in the second version. Drag in a different image, open up Trans 2 and...it's still referencing the original first Clip A.
That's not useful, as I specifically wanted placeholders for the clips to avoid having to do anything inside the Transition comp itself. I can't easily just drag in the second Clip A because then I have to cut'n'paste all the keyframes, effects etc. from the old to the new that this method was intended to avoid.
So, is this expected behaviour? If so, why it and is this useful (how?) or an oversight?
And how do I do what I need, which is to use the same transition more than once - duplicated each time is fine - with different clip references in each duplicate? I know in Composites that duplicates of planes etc. are only 'references', but creating a New Plane in the Media Bin is an actual second plane, so how do I duplicate composites and make them actually reference their embedded compos that are duplicated with them and not the originals?
It's not much use having a library of transitions if you can only use each one once per project.
I can't use Relink because you can't do that to composites, so what am I missing and how much more complicated can this get?