The file and folder selection dialog may also show a list of applications like Dropbox, Boxcryptor, OneDrive, and others. These are cloud storage providers, acting as interfaces to data stored on a cloud service. In the dialog, they appear as folders, but they are actually applications controlling access to documents stored elsewhere. While these providers grant access to single, selected files, they do not allow Notebooks to access the contents of their folders. This, however, is necessary to support search, tasks management, contexts, link management and much more in Notebooks. So, while selecting a specific Boxcryptor or OneDrive folder is tempting, these storage providers currently do not supported that.
Custom Storage Locations: When Options are Grayed Out