How to reference private repo composite actions from within other such actions

[kristofdho]

We have a private repository set up to host private actions, structured like this:

action1
├── action.yml
action2
└── action.yml

This works fine as long as the actions do not rely on each other. To simplify the setup, I would like to add a third action, that simplifies the other 2, which would need to be called like this:

steps:
  - uses: ${{ github.action_path }}/../action3

However, github.action_path is not substituted, which is also explained here: https://github.com/orgs/community/discussions/27048
This was a similar issue as well: #1419 with the key difference being that the initial action is in the same repository as the subworkflow, while now they are in different repositories so a uses: ./ would reference the wrong repository.

I get that the substitution does not work because it needs to be able to verify the source of the action ahead of time, but in this case, the caller is in the same repository as the callee, so if the caller is already allowed, it will also allow the callee.

I also know that this can be worked around by adding a self-reference like uses: org/current-repo@tag but I want the same tag to be used as the caller instead of referencing to a preexisting tag.

Is there a different way the new action can be referenced without having to resort to self-referencing the repository?