Remap Bluetooth Headset's media key [Android 9]

Setup: - OnePlus 5t, Android 9.0, not rooted - Bluetooth 5.0 headset with one media button A single tab on the media button starts the Google Voice Control / Assistant, there is no way to change a tab on the button to play/pause for example - on the headset's side. The only software solution to disable Google Voice popping up always when I press the button was to disable the Google-App completely. But this stops the media-button from working completely. After hours of trying, searching nothing worked for me. My goal is to archive that a tab leads to play/pause music.