Hi @Ragsthenos,
To add an addional column, you will need to extend the schema and then configure the display of the additional column. You can follow the next steps:
1. Extend the schema (nms:recipient): Add the custom field that you want and be sure to save it and publish it after the modifications, so the new field becomes available.
2. Update the view to include the custom field: From the part of administration inside the tool and configuration you will need to go to the group definition and specify the custom filed from you extended schema to appear in the list view.
There is no need to restart the instance cause the changes normally are reflected once you publish your schema, but if you don't see them clear cache or log again into your instance.
I leave you with some documentation that might help you.
Regards,
Celia