{
    "title": "Command_L|Command_R + Return to Backslash",
    "rules": [
        {
            "description": "Command_[L|R] (⌘) + Return (⏎) to Backslash and Command_[L|R] (⌘) + Shift (⇧) + Return (⏎) to Pipe (|)",
            "manipulators": [
                {
                    "type": "basic",
                    "from": <%= from("return_or_enter", ["left_command", "right_command"], ["left_shift", "right_shift"]) %>,
                    "to": <%= to([["backslash"]]) %>
                }
            ]
        }
    ]
}

{
    "title": "Command_L|Command_R + Return to Backslash",
    "rules": [
        {
            "description": "Command_L (⌘) + Return (⏎) to Backslash and Command_L (⌘) + Shift (⇧) + Return (⏎) to Pipe (|)",
            "manipulators": [
                {
                    "type": "basic",
                    "from": <%= from("return_or_enter", ["left_command"], ["left_shift", "right_shift"]) %>,
                    "to": <%= to([["backslash"]]) %>
                }
            ]
        },
        {
            "description": "Command_R (⌘) + Return (⏎) to Backslash and Command_R (⌘) + Shift (⇧) + Return (⏎) to Pipe (|)",
            "manipulators": [
                {
                    "type": "basic",
                    "from": <%= from("return_or_enter", ["right_command"], ["left_shift", "right_shift"]) %>,
                    "to": <%= to([["backslash"]]) %>
                }
            ]
        }
    ]
}

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.