I deleted stuff from Sharing and Permissions from a folder, how can I restore it?

Hold down the Option key when you click the Add button under Users.

I can't test it on Monterey, but it used to show all possible users. I don't know if the Staff group name was "localized" to some other name.

If you deleted and then emptied the Trash, there is no restoration available. Once the Trash is taken out, it's gone.

If it's still in the Trash can you can highlight the items and choose "Put Back". But that doesn't always work perfectly.