The content selectors for other fields have also disappeared. In version 3.6 I was using content selectors for “affiliation”, “booktitle”, “journal”, and “keywords”, none of them are working now. I also noticed that the content selector jabref-meta data was deleted from the .bib file when I updated to version 3.7. Was the content selector feature removed on purpose?
Content selectors are halfway back. Can you please try out the dev version available at http://builds.jabref.org/contentSelector/ and see if it works for you (please use a backup of your bibfile). Please report if it works for you or if something breaks.
Currently, changes to the content selectors in the GUI (new keywords, etc.) require a restart of JabRef to become visible. If the current version works, it will go into JabRef 3.8, which is planned for release next friday. We would then fix the update of the UI later on.