Maybe: If you want a track to ignore midi messages, tell it to listen only on channel 2, and have your pd code send on channel 1 (or 3, 4, etc). The tracks that should record can be assigned whatever channels are in use by pd.
I want to play along to an generative and evolving pattern - sent to the channel I don’t want to record on yet.
I guess the best thing to do is record a section of it, put in the drum/whatever pattern and then enable and go back to tweaking the generative patch again afterwards…
I still love to flag these instruments as not to record though!