If the model allows for virtual potentiometer adjustment, you can modify the potentiometer value properties. However, most simulation models calculate output based on the feedback resistors connected to Pin 4 (Feedback). If you are using the basic model, you may need to simulate the feedback loop manually by changing resistor values in the schematic.
The updated ARES footprint includes a "Thermal Pad" layer. Do not delete it. proteus lm2596 library updated
5V output from 12V input.