If you create a collection in a space or the collection page, you are creating a ROOT collection, and it shows up in the Collection Page.
If you create a collection within a collection is a NESTED collection. It does not show up in the collection page.
If you add a ROOT collection2 as a NESTED collection1, collection 2 will be inside collection1 as a nested collection, but it will still exist as a ROOT collection and show up in the collections page.
A collection can have multiple parents.
A ROOT collection doesn't have any parents and are the ones that show in the Collection Page.
Add Collection button inside a collection page, that gives the option to create a new collection or add a collection from a list.
A collection will have a parent list. And a root flag (Whether it is ROOT or not).
Questions/Pending:
Specify how permissions will work in the nested collection?
Who can create a nested collection? (Author or EditPermission)
Who can move a nested collection? (Author or EditPermission)
Can a collection be a NESTED collection of 2 ROOT collections? Is it a copy or a reference/link?
How do we differentiate a ROOT vs a NESTED collection? - A flag to indicate it is a root collection or not.