Using File > Settings > Keyboard shotcuts I was assigning Shift+X to a command. But I got the message that it was already assigned, to Effects > Video Effects > Video cleaning...
But I can find no such menu item. A search on 'cleaning' in the PDF manual finds several references to 'video cleaning', but within the program itself I can only find audio cleaning.
Nor does the use of Shift+X with a video clip selected do anything.
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Terry, East Grinstead, UK