Lock one layer to another, but not parent/link or pick whip (as far as I can tell)

[Jeff C.]

(Note: I may be using some less than ideal terminology throughout, but I'm trying to avoid mixing up what I want to do with other features that don't seem to do what I need them to.)

I have multiple layers, as expected, and most only are visible during part of the timeline. Some, I want to link or group or gang together in a way that I'm not finding. I don't want to link layer transform properties together, as is typical.

I want to connect two (or more) layers together so that when the layer is shifted along the timeline, another layer follows it. I want the transformitive properties data to remain unlinked to anything. I just want that if (for example) layer 13 is shifted over 20 seconds, then layer 12 will also shift over 20 seconds automatically. (in the screenshot, the grey and the purple should move along the timeline as one, but no other properties should be connected)

Also, the layers may not be the same length in the timeline, so it can only affect the entrance place and not the exit place.

Is this possible in After Effects currently?

[Mylenium]

No, it's not possible. You have to pre-compose the layers and move them as one block. Otherwise you have to resort to scripts or just moving stuff manually.

Mylenium

[Jeff C.]

Alright. I figured since I couldn't find anything on it that it probably wasn't possible.  Thanks for confirming!

[OussK]

Check this script it may helps you https://aescripts.com/move-to/ 

[Rick Gerard]

You cannot physically shift layer positions by script or expressions, but you can pre-compose the layers and enable time remapping, then change the start times based on time and layer index. If you create an expression that starts playback of the layer based on a multiple of the layer index, each pre-composed group of layers will shift in time based on the expression.

Here's the problem with that approach. AE is not a tool you would use to edit a movie. Unless there is more than one shot in a movie that cannot be transitioned in an NLE, AE comps are almost always one shot. If you are animating graphics or creating any other kind of animation, the length of the comp is almost always no longer than a sentence, a phrase of music, or a thought expressed in a sentence or two. 

It is almost always more efficient to render your animations or composites as visually lossless production masters and then edit them in an NLE like Premiere Pro. If you have 40 comps that you want to stack end to end, render them, select them in order in Premiere Pro and choose Create Sequence From Selected.

That's the best advice I can give you until you give us a detailed project description and your design goals.