引用自 Dr.No：

So i was wondering why, whenever you are on offline mode (no internet connection to cpu) why can't you enable/disable workshop items like mods? Seems like a rather simple feature.

Because to enable a mod, it needs to be downloaded from Steam servers and Steam can't download stuff while it's offline. Most likely when you disable a mod, Steam needs to verify that your game is intact after mod removal from Steam servers.

CRCs have to happen, and those only happen while you're online...