subsequences triggered by contact ACTIONS (not labels) - ie: (opened, replied, etc.)

I would like a way to trigger a subsequence based on the ACTION of the contact.

For example, I would like to send a little starbucks gift card to anyone who OPENED my email but did not reply or take a meeting.

Currently I can't find a way to do this in Instantly.ai without having to create a totally separate sequence based on a hand exported/culled csv list which is very ineffective b/c I would have to do it daily to keep the right cadence/timing? I'd like them to flow continuously into each other.

Note I can see that I can do a subsequence based on how they are LABELED (interested, not interested, etc.), but I can't find a way to do it based on their own actions (opened, replied, etc.)