I notice something strange when I save formats for Libraries (root) and Collections (root) folders.
First, I save formats, lib:// (library.off) and coll:// (collection.off) are add in xml files.
Now, open Prefs and Ok button.
Xlm files change to Libraries and File Collections.
So, formats are not use for these folders.
Now, save again formats for Libraries and Collections, there are 2 items for Libraries and Collections in Prefs and xml files.
Thanks for the report. This has been fixed for a future version, although probably not 11.18 as the change will need testing for a while.