I thought that Zotero would be adequate for referencing in my assignments, but sadly it does a really lousy job with regards to generating a bibliography for PDF files and it also seems to have flaws in terms of how it generate references in APA style, so I am left using EndNote X9. Is there a means of integrating EndNote X9 into LibreOffice in a similar way to the Zotero extension enables this for Zotero?
Please check the Compatibility and System Requirement at https://www.endnote.com/product-details/compatibility/, which states, that EndNote does only work with LibreOffice 32-bit version on Windows and not supported on macOS at all (which makes me feel, that the support for LibreOffice somehow is of secondary importance or is about to run out - but that’s just my gut telling this).
I had no difficulty using Endnote version 20 from my LibreOffice v6.4.X. Apparently EndNote will NOT work though with 64 bit LibreOffice 7.X so i had to roll back a version or two. Maybe it will work with 32 bit LibreOffice 7.X?
In Writer, go to Tools, choose Extension Manager, Add, then navigate to a file called endnote.otx. It will be somewhere in the Programs Files (X86) folder. In my case it was under EndNote20/Product-Support/CWYW. Choose the add on. You will probably have to restart LibreOffice. Should also work with EndNote 17.
Note that, in my experience, it is not a good idea to swap odt docs with EndNote field codes between Microsoft Word and LibreOffice. Stick with one program.