Refer to the sections for Compress Library for EndNote X and later users: "You can save your complete library (the filename.enl file as well as its associated .Data folder and all of its contents) to a single compressed filename.enlx file in order to easily back up your library or send a copy to a colleague. Later, you can easily restore (unzip) the compressed library with EndNote." Includes video: In action: EndNote 20 Compress Library
Selected measures to ensure smooth operation of EndNote include: libraries should never be stored in cloud-syncing applications (e.g., Dropbox, iCloud) or shared on network drives - either may cause corruption (a read-only copy of the library may be stored on a network drive, but with the original on the hard drive). Additional information about cloud storage
The Importance of Keeping the .Data Folder With the .Enl File