First thank you for sharing your skill in the logic macro land.
I use mainly Logic for Post-production and I am constantly opening mp4, usually they all have sound embeded and Logic X doesent auto mute when importing a Movie so I made a simple macro to Mute the video when it's imported to a Session that can be easely be linked to a streamdeck button, or modded to be executed by a keyboard key press. Mind you that the same principle applies to use your keybindings in the Green Actions, hope it helps anyone.
When pressed once it mutes the video, when pressed again it un-mutes it 
Logic X - Video Mute.kmmacros (3.2 KB)