In seventhings, groups are the tiles in which the object fields are arranged in the detail view of the object. For more information, see this article: What are groups?
To create a new group, simply create a new object field and click in the group field with the mouse. Instead of choosing one of the existing groups from the dropdown, just type in the text box. After you have given the name, the new group is already created.
Tipp:
To delete groups, simply remove all inventory slot assignments to the group. If there are no more inventory slots associated with the group, the group will be automatically deleted.