[REQUEST] Favorites list of Nodes_groups

**Is your feature request related to a problem? Please describe.**
I Need to save in local a groups of nodes for using that in other projects, but i dont want see this in the NodeTree List

**Describe the solution you'd like**
Create a sub menu "Favorites" in Add Menu and visualize here the nodes groups saved in favorites.

**Additional context**
If i save many groups, and this all saved groups appear in then NodeTree List creates a lot of confusion.