If a contact no longer matches a group, you can remove it from the
group. The contact itself is not deleted, it is just no longer a member of the
group in question.
Select the required group from your list of contacts. Activating
Groups filter helps you find it faster.
The group view (on the right) shows a list of the group members.
Hover over the group member you want to delete.
A minus sign (-) is displayed to the right of the entry.
Click theminus sign.