I'm referring to the actions of setting an automatic deploy or triggering a manual deploy in this UI:
Is it possible to do it from the Heroku CLI?
Like through the API, through the Heroku CLI command, this is also impossible. This was confirmed talking to Heroku's customer support.
I can't avoid the fact that this answer is essentially the same as the answer to the other question, one was focusing on the API and one was focusing on the CLI, and in both cases it's impossible. I'm adding this because I was told I'm not allowed to post the same answer to two questions. The two questions are different, but they are both impossible, so they have the same answer.
Here's the other question in case you are curious: In a Heroku pipeline that's connected to Github, is it possible to configure automatic deployments from the API? what about manual deployments?