Currently only single .blend files can be "mounted" as asset repositories in the Preferences.
Directories with .blends should be "mountable" as well.
There are however some design questions for this:
- Do we reflect the directory hierarchy in the Asset Browser (ie show sub-directories)?
- Should all assets from all .blend files inside a single directory be displayed in a linear list, or would we then display the .blends and then allow entering them, like the regular File Browser on Link/Append?
- Should we limit the "deepness" of the hierarchy (ie limit the number of recursions)?