This is a good – but difficult – question. TW tries to give anyone the possibility to do what developers do …
My clues and associations:
https://github.com/Jermolene/TiddlyWiki5/graphs/contributors – gives an overview over important contributors to the core. You can click the names to see what they might call themseves e.g. Jeremy seems to be the “Creator” of TiddlyWiki …
The most active few could in my eyes be called Core Developers, among them pmario and tobibeer.
Then we have many Plugin Authors, at least one TW-Professor (Steven Schneider) and the most helpful Community Members one could wish for.
Some provide advanced Wikitext-Solutions, others master Javascript-Macros and -Widgets. Some develop in Single-Page-Wikis, others on Node.js. Some use Github, others don’t.
Sometimes people that find creative solutions are called TWizards.
Now you have some keywords to put in a matrix :–)
I hope that helps a bit, even if I do not have a list of generally accepted terms but only a vague idea that there are infinite shades of gray.