iOS supports contact groups in CardDAV (iCloud, Google, other) contact accounts. In Mail and Messages, you can type in a name of a contact group in a recipient field and it is automatically expanded to all the contacts in the group. In the built-in Contacts app, you can see groups and filter the list of contacts by group, but you can NOT actually manage these contact groups.
Enter Interact. Interact unlocks the ability to create, delete and manage the members of contact groups on iOS.
Note: Interact will only manage groups in the default contacts account, as configured in iOS Settings, and only if that account is a CardDAV (iCloud, Google or other) type contact account. Learn more about Contact Accounts and Interact.
Browsing and Editing Groups
At the top left of the Interact's contact list, a group button displays the currently select group (or "All" if no group is selected). Tap this button, or swipe to the right anywhere on the contact list to display the group list.
Tapping on a group in the group list will select that group in the contact list and hide the group list. Groups can also be added, searched, and the "..." actions button used to edit or delete individual groups. Deleted a group will not delete the contacts contained in that group, only the group itself.
The group list is divided into sections by contact account. Interact can only create and edit groups in the system's default contact account, but other accounts are displayed and can be selected. Each account also has a custom "All-[account]" group which will filter the contact list by all contact in that account.
Add and Remove Group Members
There are several special query based groups, such as those that list "All" contacts, or all contacts in a specific account. Members cannot be added and removed from these groups, but groups you create can have individual contacts added and removed.
To manage members of a group, tap on the group in the group list to select the group in the contact list. When a group is selected, the Add Contacts to Group button to the right of the group name is enabled. Tapping this button will bring up a searchable list of contacts in the same account as the group. Groups can only contain contacts from the same account as the group.
In this contact list, tap row to select contacts, then tap "Add" when you are ready to add the selected contacts to the group.
Contacts can be removed from groups by tapping the "x" button on their contact in the list. Removing a contact from a group will not delete it, only remove it from the group. To remove multiple contacts, select them in the context and use the "Operation" button (see below) to remove all of them at once.
Manage Individual Contact's Group Memberships
An individual contact's group memberships can also be managed directly from the contact's action view. Tap the "..." actions button on the individual contact, then the "Group Memberships" button. In this view, tap groups in the list to toggle membership.
Create Groups with Operations
When contacts have been selected in the contact list, there are operations available in the operations menu to create a new group with those contacts as members, or add the selected contacts to an existing group.