Is it limited to mono-hierarchies or is there a way link pieces of informations to multiple parents? Maybe for something like tagging? It's particularly useful for organizing tags in a thesaurus.
It does not allow direct sharing of sub-trees, as in a single tree displayed and updated in 2 locations. It does have an easy facility to jump between cells with the same text, which is a form of linking. It also has tags which can be used with this.
Shameless plug, I made https://www.knotend.com which is a keyboard-first directed graph editor. Supports trees and directed graphs (multiple parents).