if you can select and move the parts of the prop (with one load) about the scene, then you can Choose say the chair and Click
Edit > Memorize > Object
then go to the prop page of the library and click the PLUS sign to save.
Be SURE to click the selection button because the default is to Select NONE
And SAVE
Otherwise, it's the same answer you got for your previous question... the Grouping tool!

;>

Andy!