I have not used RP Pico, I have used RP 3B with Raspbian.
Bluetooth setup was a bit tricky, you can refer to these examples to see if you can find any ideas.
http://kio4.com/raspberry/31_bluetooth.htm
BTW, a Slider extension:
https://community.appinventor.mit.edu/t/free-open-source-slidertools-bit-of-useful-feature-for-sliders/17459