Fix drag and dropping entries create a shallow copy

CHANGELOG.md

@@ -33,6 +33,7 @@ Note that this project **does not** adhere to [Semantic Versioning](https://semv
 - We fixed the usage of the key binding for "Clear search" (default: <kbd>Escape</kbd>). [#10764](https://github.com/JabRef/jabref/issues/10764)
 - We fixed an issue where library shown as unsaved and marked (*) after accepting changes made externally to the file. [#11027](https://github.com/JabRef/jabref/issues/11027)
 - We fixed an issue where drag and dropping entries from one library to another was not always working. [#11254](https://github.com/JabRef/jabref/issues/11254)
+- We fixed an issue where drag and dropping entries created a shallow copy. [#11160](https://github.com/JabRef/jabref/issues/11160)
 
 ### Removed
 

src/main/java/org/jabref/gui/frame/FrameDndHandler.java

@@ -105,7 +105,10 @@ private void onTabDragDropped(Node destinationTabNode, DragEvent tabDragEvent, T
             }
 
             if (hasEntries(dragboard)) {
-                destinationLibraryTab.dropEntry(stateManager.getLocalDragboard().getBibEntries());
+                List<BibEntry> entryCopies = stateManager.getLocalDragboard().getBibEntries()
+                                                         .stream().map(entry -> (BibEntry) entry.clone())
+                                                         .toList();
+                destinationLibraryTab.dropEntry(entryCopies);
             } else if (hasGroups(dragboard)) {
                 dropGroups(dragboard, destinationLibraryTab);
             }