I'm looking to have a Dynamic 'Reply To' for a notification when an entry is saved from a form submissions.
I'm using the below which is what the field is named in my form, but it seems it's not allowed?
Ran into the same issue, asked the support team, and they confirmed it's a bug.
Workaround is to comment out this line: https://github.com/barrelstrength/craft-sprout-base/blob/v2/src/app/email/elements/NotificationEmail.php#L481
Tried it and it works fine.
They said it would be fixed in an upcoming release.