Hi Mick,
If you minimize the Upload progress window after an upload session, then the next upload session will not automatically open the Upload progress dialog. If you go to the Window menu, the bottom entry should be for the last upload session. Clicking this will open the Upload progress dialog.
If you close the Upload progress dialog after any session, then the next upload session will open a new Upload progress window without any of the previous upload history. Does your Catalina Mac behave the same?
--Bob