+ AA6YQ comments below
You could also put an exclamation mark (!) in front of the call sign. That way those call signs would go to the top of the log so they're easy to find and you can leave Flag Invalid Callsigns checked in case you do maybe miss type a call and they would still be flagged.
+ Yes, that will work, but you must remember that you prepended the ! when searching for callsigns with SQL. For example, you'd have to use
CALL = '!WAR'
CALL LIKE '*WAR'
+ You'd also have to prepend the ! when using DXKeeper's Callsign filter.