Excellent idea! It is just a beginning of amazing upcoming things (userscripts/ addons). It is too soon to think of groups (categories) of userscripts or add-ons, but I believe when suggestion from community become larger, OP should sort them out into groups (categories). To clarify, some sort of groups (categories) like:
- Forum UI
- Archive tool
- Signature screening tool
- Flag screening tool
- etc.

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BTW, you reminded me that months ago, I saw addons for Bitcointalk Theme, there: ✔️ GREEN THEME/STYLE for Bitcointalk.org | 2019.
Suggestion:
Orginated from that topic, I created my topic: [Guide] Viewing images without quoting posts/ OPs.
Can you (or others) can build an userscript to view Images without quoting posts/ OPs, and don't have to spend a little time to visit post histories?