Expanding Collection - How do you do it?

Where is your music stored?  Internally or externally?

I'm guessing you have them on an internal drive.

I keep only my top played tracks on my internal drive and export everything else to external drives.

Yep I'm storing everything internally. I'm just thinking if I could continue to run Rekordbox on 2 machines if my library is on 1 external drive?

This is a great example of why it's a good idea to store your content externally, not only can you expand as required but you're not pressuring your operating system for space as you fill the drive.

The best course of action would be to move the entire folder structure, as-is, to an external drive, remove the music from the internal drive, then relocate the entire collection once.

While this doesn't allow for sharing of the library between two computers (as the library file itself is still stored internally), you'll at least have all your music on the external drive and you can move that between machines.  I've forgotten if I had a guide on the forums for a portable library...