The wonderful, and now obsolete, Vision sequencer had a MIDI Relock command. You could record a sequence in hopelessly broad rubato or with intricate polyrhythms, then tap in a line that showed where you wanted the downbeats. The command would reclock the jumble of notes into proper measures as needed.

If you're, say, improvising 11 against 19 beats, there's no other way that I know of to set the file up for notation.

Early versions of Finale had this feature. They called it a tag line.

I can't be the only musician who ever wanted to transcribe polyrhythms!

Can anybody suggest how to do this with current software?

Grey Otter