1. To set the Logic Pro X preset on your MPK Mini Plus, hold down the PROG SELECT button and push Pad 3.
2. Select Logic Pro X to the right of the Apple logo, then select Key Commands > Edit Assignments... to modify the preset.
3. In the Edit Assignments window, use the search bar to find your chosen Logic Pro Key Command, click Learn New Assignment, then press the button you would like to assign on your MPK Mini Plus. The Control Surface box in the bottom-right corner should display "Learned".
Note: Although in this instance, I have assigned the Play button, you can assign any button you'd like using the same procedure shown above every time.