It certainly would be possible in the future to sort by other elements in the future, but unfortunately, I suspect that the current treeview sorting code will need some refactoring to be able to support other sort methods - especially when there is a risk (as with all 3 of the examples you gave) that some records will not have these values applied.
The older sidebar treeview does have some additional settings for sorting either by title, or by identifier first, then title - however, there are known issues with these sort modes, and for that reason we generally recommend that administrators don't use them. This is also why the full-width treeview doesn't currently have other sort options.
Essentially, part of the problem is that any or all of these values can be blank in an AtoM description, and the code gets caught in some sort of loop when trying to sort records on a value that doesn't exist. There's an old ticket for this in our issue tracker
, but it's not very descriptive. The result that many users have reported is the same set of 4-5 records displaying endlessly in the treeview. Here's one older thread where I explain the issue:
We did have someone ask about possible solutions, and here's a thread with some further details on the issue, as well as thoughts and rough estimates for possible fixes:
As you can see, it's not a small issue, and therefore one that will require community support (either via code contributions, or development sponsorship) for Artefactual to undertake.