Apart from what @Yos N. writes, it's more complex.
First I recommend reading this help page - https://www.dynatrace.com/support/help/how-to-use-dynatrace/process-groups/basic-concepts/which-are-...
It helps to understand how Dynatrace detects processes in general and how it decides which of them are important.
By default, Dynatrace monitors all processes, but then you have to distinguish between deep monitored processes (code level instrumented by OneAgent) and other processes.
Code-level instrumentation requires full-stack OneAgent mode.
In general - Dynatrace monitors process availability for all known processes. The default setting is "If service requests are impacted". However, for processes that are not instrumented where deep monitoring is not available Dynatrace can only monitor process unavailability in the means on a network level (incoming network request for a previously known process that cannot be handled). If you have only cloud-infrastructure mode agent or the processes are not supported for deep monitoring, you should consider changing this setting to get process availability monitored.