Tommy Chong:
The Mendeley plug-in that you reference does not appear to exist.
You could export an RIS File designed to be imported by Zotero via the Calibre "Zotero Metadata Importer" plug-in. I am sure that Mendeley will import an RIS File too (it is almost universal). So, you could use an RIS file exported from Calibre via ZMI, but send it to Mendeley instead of Zotero.
See the attachments below to view the flexibility that is available to map almost any Calibre metadata to the RIS file.
The ZMI plug-in homepage is:
https://www.mobileread.com/forums/sh....php?p=3339192
Obviously, the RIS file will have only metadata. You will have to attach your actual Calibre book files to Mendeley using some function other than ZMI.
Zotero is open-source and free, by the way.
https://www.zotero.org/
DaltonST