Custom Field Visibility and Admin Control

I'm writing to suggest improvements for the RSMail extension features, which currently appear to have some drawbacks.

RSMail's capability to send follow-up emails is commendable. Within the follow-up list, incorporating custom fields for users to manually input relevant values is a valuable feature. However, a concern arises when users on this list can also view the manually added values in their editable subscription mailing list. This prompts the question of why these fields need to be displayed to the user in the first place.

To address this issue, it would be beneficial to introduce an option that allows admin to hide or show fields in their subscription view.

I believe that incorporating these suggestions will contribute to enhancing the overall quality of the RSMail extension.