Unfortunately not yet. The history behind our use of Redactor is a little weird. A helpful contributor purchased an open source license of Redactor for use in NodeBB (and paid quite a bit for it, too!). So he technically owns the license and allows us to use it.
Redactor didn't like that much, so they no longer offer the open source license for purchase (even though now we are more than capable of purchasing it now), meaning we (as a company) can not purchase Redactor for use in nodebb-plugin-composer-redactor. The contributor is able to retrieve new versions, however, and give it to us.
I've sent a message to this contributor and am waiting for a response 😃
If it really is just 100-150 old topics, then an nginx map makes even more sense.
I can see it from your point of view, that it's easy for NodeBB to do, although I urge you to consider that nginx is very good at what it does, and so having nginx check for an old url to redirect is quite simple.
For example, if the old forum had topics using this url: /t/<topic id>, then you could write a location block that only responded to that folder, and applied the map to redirect the user based on those topic IDs.