In my experience it should show up nearly immediately if it is going to show up. If you're not seeing them take a look at this document which lists the criteria for what should start showing up under processes (marked as important):
I'm not certain of a way to customize this but I would guess that if you had custom processes group detection rules they would show up if there was a specific rule for some variable. Not sure though, may need to wait for more input.
The basic interval for OSAgent is 10s. This is the resolution with which process metrics are captured, etc. However, the process list is reported to server once every minute and this is the 'current snapshot', rather than aggregate over entire minute. This means, that only processes that live longer than minute are guaranteed to be reported.
There is also a question of PGI importance. If the PGI you are interested in monitoring is only important due to high resource consumption, it will take 3 minutes to calculate that. But from the question itself I assume this is not a case. If it is, you can work around it using custom process monitoring rules, which are applied immediately.