You're totally right that concatenating mininotation strings is probably the simplest approach for this. In that case, you'll want to pass your string into parseBP_E (the underlying function that Tidal uses for parsing mininotation).
Also, for @staxl and anyone else who's curious: yaxu's blog post is probably the most recent complete-ish explanation, but you can also find bits of discussion in this thread, plus on the Discord innards channel, etc.