I save them in my Sketchup components. This way you have instant access to them. You can drag and drop however I suggest you create a folder first. I have one for landscape, furniture, bathroom items ETC. Before I save them I use the BIM tool to add in price and any other info I want for my bill of quantities or cost estimate.
Here is the link to all of the components on the Rubysketch https://3dlibrary.rubysketch.com/specific_search/6
have been optimized to work efficiently in Sketchup and PlusSpec.
I am not sure if you have had a chance to download this one? https://3dlibrary.rubysketch.com/entries/wall-beds-australia-next-wall-bed
it is great for space saving TIP use the interact tool and the Dynamic component attributes to change colors and to animate.
I also have been uploading construction details in 3D as they help understand how systems go together.