Native Stems support for X1 MK3?

The mod changes the qml files that define the basic x1mk3 functions. They are loaded together with every x1mk3 tsi mapping file. You can find the qml files (for all NI devices and some others as well) in the qml subfolder. To use a qml mod, you have to replace some of the original files with the modified files. Instructions on how to do this are in the same post (post#1) that also features the download links.

'Overmapping' means that you open (select from device dropdown) the tsi mapping file on the controller manager page (Preferences) for the x1mk3 and create assignments which override the qml code for the relevant knobs, buttons and LEDs. There is also a 'override' box. If left unchecked, both the original function and any new assignments for the same controls will be triggered at the same time, so always check the 'override' box.

The X1Mk2 (and mappings for it) work the same way, except the underlying basic functions are not accessible and so can't be modified. But overmapping works just the same, like the mapping file you linked to.

Get back to us with your progress. Maybe you can upload your working TSI for other users looking for help.