Your library examples are in category of
UNSUPPORTEDin the arduino examples tab.
Will fix in next release of some libraries. As you use mbed_rp2040 core, the slow PWM library to use is MBED_RP2040_Slow_PWM
If the library's examples are not shown or shown as UNSUPPORTED , move down to the INCOMPATIBLE list of examples or open directly from the libraries folder
I am also having a hard time , so the duty cycle parameter what is the value range? 0- 100 because it seem to have a double data type
It's double, so you can use from 0.000-100.000 to have better precision.