First off, loving the MX Keys. It's replaced my Magic Keyboard and I'm loving the slight dip in the keys and the better travel.
One thing I'm struggling with is applying shortcuts across apps.

My suggestion would be that it would be good to somehow be able to apply the default for a particular key across multiple apps, or maybe just one app.

For example, I have a specific screenshot tool I use so I've changed the app behind F17. However, I need to go through each of the apps I've added customisations for. I only need to update this one button for all apps.

It would be good to either have a button to apply the default across all apps or to have 'Apply default' for a particular app.

Ideally you'd be able to do this just for a particular button.