I collected ~250 entries in my database. Now I want to export a .bib file for a journal publication (~50 entries), which I collected in a group.
The journal has specific required fields for each entry type (for example: article → author, title, journal, volume, year).
If I export my publication-group to a bib-tex file, all groups (url, notes, groups, keywords, etc.) are exported as well.
Is there a clever way to only export the required fields of my group of entries?
The Quality>Cleanup feature seems to do the (unproportionaly more difficult) opposite of selecting and removing the ~20 unneccesary fields instead of selecting only the 4 required ones.
You are right, this would be nice to have and I am not quite sure how one could achieve it with JabRef currently. Since Redesign "Manage field names & content" dialog by HoussemNasri · Pull Request #8892 · JabRef/jabref · GitHub, the Automatic Field Editor you can remove fields, but it is not possible to select multiple fields at once or do an inversion as you propose. I think your idea would be a nice feature and you probably should create an issue at github, so that we can track it.
If push comes to shove, you could try to parse contents of your bib file via Regular Expressions (RegEx) and then delete unnecessary fields or retain the fields you want. Some texteditors, such as NotePad++ support RegEx. https://regex101.com/ should help.