If I import a group definition and delete one of the included certificates afterwards, the certificate is no longer shown in the group definition and therefore no longer used for encryption to that group.
This may cause confusion especially in the context of encrypted group mails. A users might not always be aware who is participant in a group mail address (as group membership is not shown in the certificate list, see also T6240) and might delete a certificate of the group. The result would be that that person would then get a mail which is not encrypted to them.
I propose
a) a warning when attempting to delete a certificate which is in a group
b) an optional column in the certificate view displaying the group memberships of a certificate