I also do this, except I modified my insert link button to insert only the tiddler title without the [[ ]].
See this discussion on how they modified their search results list to include bibliographic entries. Search results lists appear in the “create wikitext list” dropdown too.
If you’re interested in other plugins, the edit-comptext plugin does exactly what you want: completion with <<macro ", and custom filters to only show subset of tiddlers. But it unfortunately doesn’t work (and isn’t meant to work) with Codemirror :((((.
I prefer having Codemirror than cool autocompletion, so I use ctrl+L instead like @Mohammad.