This has nothing to do with Sonar in particular. This is a built in FUNCTION of Windows and is present in all Windows applications which uses the standard of the Windows MENU system. This standard you will see is
File (on the top left) and the 'drop down' you get 'new, open, save, save as etc.' This 'most recent list' of used files is held in a DATA TABLE which can be erased by going into the registry.
I may suggest not phuting around in the registry for something like this.
I see my Sonar keeps the most recent 8 in this 'clipboard'.
All applications will keep the newest saved file as 1, then pushes down the lists as you use more newly named or created files.
The issue is; why when you delete a file why Windows does not remove it off this table.
Because; it is not designed to do that.
You may find another Utility to do it or find a geeky IT person to write a script.
OR ploy your way into the Registry and figure out how to "clear the
MRU LIST for Sonar"