Currently, the custom field for AcyMailing is a unique field I guess since I cannot duplicate it.
Anyhow, the issue with it is it seems to be written assuming that a user would want to subscribe to all mailing list. There is an option to enter the ID or IDs of the mailing list separated by comma.
- The problem is: it assumes that a user wants to subscribed to all the mailing lists.
- Suggestion: Make it so that it is a standard field so it can be added multiple times or make it so that it pulls all the available mailing lists and let the user select what mailing list they want to subscribe to. Personally, I prefer the latter.