For brushes, you can save them as such. If you save them in the correct folder, the next time you'll restart Gimp they will be there ready for you to select.


For the furniture I use I actually do just what you said.
I did organize my folders (like Furniture > Beds and sittings > Beds ) so it only takes a few second to get to the right folder... I also add shortcuts so that the same object can be present in all the folder that would make sense (an alchemist table would be present under "table"; "Magic" or the "Alchemist" section of "shops and workshops". But apart from that, I have no trick.