I'd like to be able to make a new default setting for certain things using Persistence, like NoScript defaulting to Forbid Scripts Globally and forgetting Allowed scripted upon shutdown.
Can a persistent file be made to forget changes at shutdown?

I'd like to be able to make a new default setting for certain things using Persistence, like NoScript defaulting to Forbid Scripts Globally and forgetting Allowed scripted upon shutdown.
Can a persistent file be made to forget changes at shutdown?
The use case you describe is exactly why you can choose to open a persistence volume in "read-only" mode.
Unfortunately, NoScript settings are not covered by Tails persistence framework. Patches are welcome, though.