What to do when closing master and prompted to save or not savechanges to subs

[anovak]

Are there any gotchas or guidelines for when to save changes to subs
as a master is being closed? Do you have to save the subs in order
for the ParentProjectUID of the master to be propagated to the sub
after being initially inserted? Can you actually make changes (add
tasks, etc.) directly into the sub from the master or is it best to
open each sub individually?

Thanks,
Andy Novak