2.3 group membership list does not allow assignment of attributes to a membership.

When viewing a group's members the "Actions" button for each membership does not have the "Assign attributes" option.

However, if you view the user ( by clicking on the "Entity Name" column). The "Memberships" tab's Actions menu does have an  "Assign attributes" option.

Please add the "Assign attributes" option to the Group Memberships tab.