Buton selection piste

Hello, I would like to know why the button for programming “track select” is no longer present in version 3.
I am able to handle all other mappings, but for this specific command, there doesn’t seem to be a simple way to do it within the program.
Thank you for your feedback; if you know of a simple method to achieve this, please let me know—without it, this program is useless to me…