Yes, object groups are a thing in Fusion. They're called qualifiers and can be found in the "Events" section of the properties panel. You just need to click on the blank area next to the "Qualifier(s)" section and an Edit button will appear. Upon clicking this you can select "Add" from the box that pops up and select a qualifier from the "Add a qualifier to an object" menu (it doesn't matter which one you choose). After you choose one you can then create events which target the qualifier group (it'll show up in the "New Condition" menu with icon of whatever qualifier you chose).