Searchwikis plugin uses index (dataTiddler) to search multiple external Tiddlywikis.

https://kookma.github.io/TW-Searchwikis/

It has two parts

1. An indexer, to build an index of all tiddlers in an external wiki
2. A search tool to search indexes and display a link to a tiddler found in an external wiki

Then one master wiki can host many index tiddlers and lets to search several external wikis through index tiddlers.

Searchwikis enable to have a central wiki and search all other wikis from one place.