writer DDE link edit problems

Hi,
in writer I cannot select any entry of the list displayed using Menu/Edit/Object or Menu/Edit/“Links to external files” in order to edit it. The list has at the bottom a “Modify” button, but no selection from the list is possible. Clicking on any entry of the list (in my case DDE objects) the entry does not remain highlighted (selected) for further operations.

LO writer 6.4.2.2