@ekimekim Eh, I just tell Steam to set up a second library. Then again, in my case I keep some games on an HDD and some on an SSD. Exactly which goes where is semi-arbitrary, so my system does not help.
@ekimekim Ah. I'm pretty sure it's directory-based under Linux. Either that or it's mountpoint-based. The automatic prompt suggests entries based on mountpoint, but I think it'll dump it wherever you want (under a Steam directory).
@captainspam I did the same on windows up until recently. But this seemed simpler than maintaining two libraries.
I didn't actually bother checking if steam supports multiple libraries on linux - since on windows it's drive-letter based and linux doesn't have that concept.