DIY shifter for Bkool Smart Bike

Hello, I am currently using my Bkool Smart Bike on Zwift, which works great in ERG mode during workouts. However, I am unable to do races as the smart bike does not have an electronic shifter built in. I can use Bkool’s mobile app to shift gears, but this only works when I am using the Bkool simulator.

Therefore, I was wondering if anyone has experience making and coding a shifter to change gears on the bike, without having to use the Bkool simulator?