Hello Erik! I will answer your questions in the two parts it was asked.
1. There is not an interaction window built natively into the UI of prefect, but you can provide a stage where a notification can be signaled when
a flow is completed, and then a user could go into the UI to manually kick off another flow run once they have manually validated.
2. You can have
states for your flow runs, and many people use that for states or events to conditionally kick off other flows
Here are more examples on how to handle this interaction
https://docs.prefect.io/concepts/states/#return-a-prefectfuture
Hopefully this was helpful!