If I understand the question the answer is yes. I think you're asking if you can retry portions of a job, like if a task breaks but doesn't exit with an error, thus causing the rest of the job to continue.

In this case, yes, you can retry a task in the middle of a tree of tasks, and retry all the children tasks as well. This will leave some tasks untouched (the parents and peers) and retry the children in the same order as the first time.

If a task in the middle of the tree fails children tasks will not run until it's been skipped or successfully run.

Retrying children tasks would be a great job for a GUI for Norc because then you could choose which children tasks to retry interactively from a web app or somesuch...