Reviewing my bookmarks I've found this interesting site containing example code:
Dynamic Tree Structure LWC, created by Lakshay Katney.
It contains sample code that shows how the lightning-tree LWC can be used.
The Apex controller retrieves tree levels recursively (accounts with children accounts, grandchildren, etc with related contacts, opportunities and cases).
The Playground | Playg.app site is a free and public store of reusable solutions for Salesforce that have been shared by other users.
It was co-founded by Shantanu Srivastava, Darshan Farswan, Shailesh Gusain, Nitin Goyal and Lakshay Katney in 2019.
