Unless anything has changed recently, the best thing you can do with Mendeley is switch to another reference manager. Here is a quote from one of my many posts about Mendeley:
Petition Mendeley to support a writing workflow in anything other than MS Word? I asked last year helping someone with their workflow; the response I got back was pure generic corporate BS about valuing my feedback and striving to make X better for everyone blah blah. The older desktop app did offer the use of BibTeX keys, but the newer web-as-desktop app even removed that. My recommendation is switch to a better reference manager, or sign your pact with the devil and downgrade to writing exclusively in MS Word…
In text citation Mendeley