Currently we have an open_datatree function which opens a single netcdf file (or zarr store). We could imagine an open_mfdatatree function which is analogous to open_mfdataset, which can open multiple files at once.

As DataTree has a structure essentially the same as that of a filesystem, I'm imagining a use case where the user has a bunch of data files stored in nested directories, e.g.

project
    /experimental
        data.nc
    /simulation
        /highres
            output.nc
        /lowres
            output.nc

We could look through all of these folders recursively, open any files found of the correct format, and store them in a single tree.

We could even allow for multiple data files in each folder if we called open_mfdataset on all the files found in each folder.

EDIT: We could also save a tree out to multiple folders like this using a save_mfdatatree method.

This might be particularly useful for users who want the benefit of a tree-like structure but are using a file format that doesn't support groups.