Such a small improvement, but somewhere I have to show my work :
Maybe here I could find a helping hand in building a new editor for opendungeons : https://snapcraft.io/opendungeons please choose an edge channel/version.
To copy/ paste a bits of map just mark it with mouse and then Ctr-C, drag around the map , and then Ctrl-V.
The only cons I can admit is : the recently used level map files' list is not actualized when you do enter the editor from Editor->Load->Map main menu .... but this is going to be improved in next versions I hope.
Write what the editor lacks or even about the bugs ...