Currently however, selecting a marker causes its popup to appear, making the DEL keypress go to the edit.
Bug is invalid.
Deleting works just fine when the marker is selected and the popup is closed, e.g. using the ESC key.
Deleting the marker by pressing delete with the popup open is something I don't think we need to support. It's would also require that the focus not be on the QLineEdit when the popup shows because otherwise, the text is deleted instead of the marker being deleted.
However, clicking on a marker and typing away to change its name is the primary purpose of the marker's popup while pressing delete is expected to be used muss less often in comparison.