This is mainly about making deeply nested templates with lots and lots of }}}}}}}} easier to navigate, e.g. via rainbow coloring or whatnot.
To do:
- Look at the CodeMirror documentation to see what's even possible
- Look at MediaWiki-extensions-CodeMirror
- Check how the integration wiki core works
- Check where the implementation (of the wikitext syntax highlighting) lives
- Talk to WMF ComTech (sync, ask open questions)