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...
I was little confused because it seemed like norc would only start jobs at the top level.
Jobs start with any tasks that return True when asked due_to_run(), which can be schedule, parents' status, etc.
Glad I could clear it up!