Group
Groups connect multiple objects.
You can create a group by selecting multiple objects and pressing ⇧ G , or right-clicking and pressing folder at the top of the context menu.
When you export a building, any group will result in an individual STL file. You should therefore create groups that fit your printer's build plate size.
While you are building, groups can come in handy to get some structure into your hierarchy and to modify multiple models at once.
Groups always rotate and scale from their center.
To select an individual object that is part of the group, hold down Alt before clicking or use the hierarchy menu.
You can add objects to an existing group by selecting both the group and the objects you want to add, then right-clicking and pressing the create_new_folder button at the top of the context menu.