Enhancement: Group data files in a folder under the folder id

[michaeltlombardi]

Is your feature request related to a problem? Please describe.

After I schematized my data types and began adding my data to the site, my data view on the dashboard became harder and harder to quickly find, especially when file names conflict (even though they're different data types in different folders).

Describe the solution you'd like

I would like for the data files defined in a data.folders entry to be child items in the "Select your data type" menu for that entry. If the id for a folder is Foo and it contains the bar.yaml and baz.yaml files, I would like those files to be listed under Foo as collapsible child items instead of just their file names in a flat list.

The entries in that menu already include an arrow, though the arrow doesn't turn or change colors on selection (the arrow and the text both look a little brighter, though, when editing that file).

Describe alternatives you've considered

N/A

Additional context