You have to remember (or going) trought every folder to detect new adds (by date) and the drop to engineDj. Maybe I have 200 tracks in 50 diferent folders, sometimes under year structure, sometimes under collection, sometimes under tools, etc. I try what you’re saying but not works for me. My way, just have to lisen, put where corresponds, run my script to tag and done. Just need folder browser read some tags from file (like filename) and show on it. Not demanding so much.
Maybe if Denon sometimes in a distant future adds the Watch Folder concept in EngineDJ, I change my mind and put all my library into collection/crate to autoupdate library on startup or on demand only with new changes.