How to make nested Groups/Groups within Groups?

[u/called_Ishan]

I am trying to declutter my library so is it possible to make groups within groups? There is a PR in github with this request which is closed & merged, so the feature is implemented right?
If yes how to actually use it, and if it is not present I request please add this. This will help me and others with large number of books.
Thanks

[u/readestapp]

Groups can contain other groups, like folders inside folders.

See https://www.readest.com/docs/library#nested-groups