@fiduswriter JabRef's internal format is just #bibtex We already have one for Citavi with a test case and some others, I think Mendeley is not yet supported because you can export it as a bib file
All other import formats are implemented here: https://github.com/JabRef/jabref/tree/main/jablib/src/main/java/org/jabref/logic/importer/fileformat
We also support integration with #LIbreOffice





