Feature request.
I'm on a multi-animal setup, training with top-view mice videos, without using the identity layer ('identity = False'), because of the similarities between mice. When running DLC with two mice, I run into an identity swap that I believe would be very difficult for DLC to detect automatically, therefore I plan to build a GUI to correct these swaps manually.

Here is an example:

Describe the solution you'd like
I would like to add to the existing "Refinement Tracklets GUI" a new button allowing fast correction of identity swaps.

Pressing this button swaps 2 animal identities from the current time until the movie ends.

Example: after pressing the "SWAP" button, we get:

If working with more than 2 animals, we might need additional controls to specify which animals have an identity swap.
We could also add more buttons such as "NEXT ANIMAL CROSSING" to jump to the next potential swap due to animals crossing.

Describe alternatives you've considered
I also considered making a separate GUI dedicated to identity swap, rather than adding new features to the existing Refinement Tracklets GUI.

My questions
Can this be added to DLC? I would be happy to try developing it myself. In this case, probably I'll need help to know which code to edit, what to pay attention to, etc.
Furthermore; I'd appreciate any advice for doing it in a way that I can later push this new functionality to the DLC project.