Cannot removed linked XD document
I have an XD document that links to another XD document (a style assets document). This was set up the old way before CC libraries were added to XD — as explained on this website: https://letsxd.com/videos/linked-assets. Basically the style library document is saved to the cloud, and then it can be set up as a linked document in another XD document, and all of its components and styles become available in the new document assets.
The problem is that I cannot figure out how to un-link that document. I want to swap out the old style library for a new one. But I cannot delete any of the individual assets that are linked (including ones that were not used), nor can I find any way to unlink the whole linked document. It seems like there should be a "Remove linked asset library" control somewhere, but I cannot find it!
I don't want to delete the source file, but rather remove the connection.

