In the "Citation relations", if there is no DOI, offer a "link" to determine the DOI.

1. In the text shown "The selected entry doesn't have a DOI linked to it. Lookup a DOI and try again.", the text "Look up a DOI and try again." should get a "hyperlink" triggering the lookup.
2. When clicked, the text should change to "Looking up DOI..."
3. If no DOI found, notifiy users "No DOI found" and change to initial state.
4. If DOI found: Use it for citation relations

Note on Engish language: It needs to be "Look up" since its a verb. See https://english.stackexchange.com/a/555267/66058.

Hints:

• Regarding hyperlinks, you can see at org.jabref.gui.WelcomeTab#createWelcomeStartBox how this works in principle.
• It is necessary to split up the localiatzion string. See https://devdocs.jabref.org/code-howtos/localization.html for localization hints.

Add following paper to JabRef:

@InProceedings{Edwards2004,
  author    = {S. H. Edwards},
  booktitle = {Proceedings of the 35th SIGCSE Technical Symposium on Computer Science Education},
  date      = {2004},
  title     = {Using software testing to move students from trial-and-error to reflection-in-action},
  pages     = {26--30},
}

Click on "Citation Relations"

Now switch to "General" and click "Look up DOI"

See that a DOI is dermined:

Then, "Citation relations" should work (if there was no network error)