I don't think there's a lot to say about it. You can get a six position switch as a replacement part. If you have a X9D plus, there's an additional S3 port where you can connect the switch, but you have to drill a new hole somewhere.
If you don't have the plus or don't want to add a hole to your Taranis case, you can replace one of the existing pots.
The switch basically works like a pot with six fixed positions.