Fixture Groups allow you to group various Fixtures together.
Each Fixture can be assigned to multiple Groups.
Groups are used in multiple places. You can apply a Block Stack onto a whole group, reference them in spatial Blocks and more.
Assigning and removing Fixture Groups is done through the Schematic view.
To add a Fixture to a Group, open the property inspector and press the circle with Add. The text may be hidden when you're zoomed out too much but it will work the same.
Then either select one of the existing groups or write a new name and press enter.
To remove a Fixture from a Group, middle click the circle representing the Group.