Alternately, when you export you can check 'include existing groups in polygon groups'... if each chair and table has it's own group it will reimport all as one consolidated group object but will retain it's pre-existing named groups. Poser will append a number to each group name however*, which in certain circumstances would be undesirable. For your purposes it wouldn't be an issue I think. You can then spawn props and separate without assigning new groups.

• Poser keeps track of things this way if you have multiple duplicates of a group in a scene.