Currently, when creating a new dimension, it's generated using the default namespace, which is minecraft. That may create confusion since dimensions are saved inside a folder named after its namespace.

Therefore, my suggestion would be changing the default namespace to either scarpet or carpet, allowing to change it by manually specifying a different one.

A problem that may arise is that in_dimension (and other future dimension getters using dimFromValue) won't accept Scarpet dimensions by only path (name), since its namespace won't be minecraft, and I don't think it's a good idea to change the default namespace in there, even if minecraft: dimensions are already covered. Solutions may be making docs clear about the namespace or checking with two namespaces in dimFromValue, which I don't think is ideal.

Another problem is, well, existing custom dimensions without namespace would need to be moved.

custom_dimension isn't heavily used though. I've literally searched in every github repo which included "scarpet" in its name or desc or was tagged "scarpet" (there are 5 pages as of now) and didn't find a single match, so I don't think adding it would hurt many current apps, if any.

Closing since custom_dimension is deprecated since latest release.