1. Create a new bib file
2. Add new entry for https://doi.org/10.1016/j.cl.2018.01.004
   
3. Add new entry for https://doi.org/10.1016/j.cl.2018.01.004

See that dialog is the same:

Wish: Below the DOI identifier there is a hint displayed:

"Entry already existing in library. Select entry."

"Select entry." is a Hyperlink. It selectes the entry in the respective library.

Hints:

• org.jabref.gui.LibraryTab#showAndEditcan be used to jump to the entry

Next step

After the initial functionality is made, one can implement it to handle more than the currently opened tab

See org.jabref.gui.search.GlobalSearchResultDialog#initialize at resultsTable.setOnMouseClicked(event -> { how to search an entry in any tab.

The hint should say: "Entry found in library X. Select entry."