@
allowingtoo - the 'ghost screen' at termination was introduced when "Library Closed Plugins" were introduced. So far there only one Library Closed PI ==>>
Save Composite Custom Columns.
IIRC the 'ghost screen' provides a 'surface' on which a progress bar/wheel can be displayed, otherwise it's transient.
Save Composite Custom Columns supports the operation of Calibre Companion on Cloud storage.
BR