Hi @BitSeeker.
Support for specific programmers is implemented in the codebase of individual Arduino boards platforms, not in the Arduino IDE application itself (the IDE application only needs to provide support for the general purpose framework):
https://arduino.github.io/arduino-cli/latest/platform-specification/#programmerstxt
The "MegaCoreX" platform has support for the PICkit 5:
When using one of the boards of that platform, you can select Tools > Programmer > PICkit5 UPDI from the Arduino IDE menus.
All the "MCUdude" platforms (MiniCore, MightyCore, MegaCore, MegaCoreX) have support for the PICkit 4. Likewise for DxCore and megaTinyCore. I don't know whether that support also applies to the PICkit 5.