@DaveGifford
Hi David,
NO, it is not! I can say it is not even similar to subsume!
It is a section editor! This concept comes from dokuwiki and wikimedia!
It will work later using a simple field value or tag!
Including other tiddlers in a tiddler with an edit/link/button is a common knowledge in Tiddlywiki and you can find it in many user wikis out there!
TW-Scripts has bunch of folding editors, inline editors and tools to include other tiddlers in a master tiddler! BUT none of them can do section editing!
So this is not re-doing subsume! I think you post your opinion before you test the code I shared!