This is no longer relevant for my problem, but taking the opportunity to share my opinion:
While this works nicely for Gmail, I do expect to connect the IMAP Email to a protonmail bridge, this same solution won’t work for that use case I believe. It would be nice to have an IMAP manipulation node in the future. I’m not sure if node-imap allows for search + delete labels operations, but that could be a start, even if we have to pull emails twice (once to receive the email, and then to search and mark as read)