I know that you can export a single reference to a .bib file, but it would be very useful to have a "right-click copy bibtex entry to clipboard" function. That would make it much easier to build up a .bib file for a manuscript, entry by entry.
I would love to have this feature, I used it all of the time in Papers 3.
This feature would be amazing!
Definitely a much needed feature, above all for those that have very big libraries. Although one can create a specific collection for a paper and export the .bib file, it is very common to just build the bib file incrementally. Also, usually few corrections are needed to the bib entries to optimise the reference section, exporting all the bib at once forces to re-do the correction every time the file is exported.
Copy-to-clipboard is the best possible solution.
I agree, it is a very useful feature in Papers 3.