How do I separate assets in an asset pack?

On downloading asset packs, I haven’t found an efficient way to separate them into individual .fbx files without manually separating each piece and creating bounding boxes from scratch, which is very time consuming considering I have asset packs that are more than a dozen pieces, some of which are rubble and other decorative pieces. Are there more efficient ways to separate assets from packs that are all in one .obj file?

I’ve tried many ways of setting up folders to hold fbx files from asset packs. I made a list of items in packs I like to use and when I want to use them I call up that pack and migrate the asset. I also set up “dummy” projects with favorite assets in them. Exporting / importing assets to files seems to work at times. I’ve done this with animations. When you import you can retarget them to the skeleton you are using without having extra skeletons (in your project) setting around doing nothing.