Everyone works different but what works for me is, when I first purchase a new set of models I place them into my assets directory somewhere that suits in my library. General rule of thumb when working with 3dsmax is, once you put it somewhere dont move it unless you want to go through the below process every time for every model.
Then I open the model I need, relink the textures using
Colins Bitmap Relinker script. It saved me so much time I had to donate some money to the guy. Save the scene then bring the model into my scene. From here on that model is always pathed correctly so no need to fuss about with missing textures etc. Next time I need a model I do the same thing -> open the scene, relink the paths, save the scene. That way each time I open the model the paths are always correct which means I can just copy/paste or merge.
You can also batch do this with other software such as
Design Connected - Connecter (which is also free). This is also a great way to relink all your assets from each set of downloads so that when you file > merge they just come in as they should.
Generally I dont change their folder structure, I just use those 2 tools to do whatever I need since I dont really care how its structured aslong as its where it should be in my library and all the assets are not missing (linked/pathed). Then I can just do my job, file > merge, place tree or place in some scatter etc. Or with Connecter if you spend some time organising it nicely you can just drag it in from the UI.
Also depending on what tools you use, you can build a cool automatic library. For example Forestpro gives you the ability to save a bunch of assets (as long as they are pathed), preview image, all as one scatter. Then you can just go to the ForestPro library, pick your favourite custom gardens, forests, whatever you want really and just place it in the scene. Select your area and apply. I even use Forestpro for cars in carparks, feel free to use your imagination, hundreds of different furniture layouts in buildings... why not? :D
