I think I've seen this feature on other forum software (Discourse maybe) and definitely on Stack Exchange. You basically are not allowed to tag a topic unless the tag already exists.
@baris Thanks! Yes, memory still looks good.
@julian Well thank you for your answer anyway 😊
I'll keep checking this topic in case someone comes up with an idea !
Did you get this working @Aditya-Tripathi ?
Superb, thanks @julian much obliged.
Feel free to add a pull request for this if you haven't already 🙂