I’m living the small SSD life so I already have ~/movies and ~/music SYM linked to an external drive. I have about 100 GB of books taking up precious space. Is it safe to SYM link ~/Library/Containers/com.apple.BKAgentService/Data/Documents/iBooks/Books to an external drive as well or should stuff in the library folder stay put?
I’ve done this with other apps in ~/Library/Application Support/ without problems. I don’t see why it should cause problems but there may be unforeseen issues with permissions depending on how the external drive is set up.