Fix the mutiple modifier to be mandatory bug & add optional ⌘L 
Fix the mutiple modifier to be mandatory bug & add optional ⌘L 

I've actually managed to mess it up with this pull request, https://github.com/pqrs-org/KE-complex_modifications/pull/600. (I'm sorry 😅)
The PR was suppose to make Command_L optional but instead it made both L and R mandatory at the same time.
So this PR fix the issue and make Command_L optional, too.
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