TinkerCad provides a simulator.
Sign up for an account and log in. Lost? Click on the TinkerCad logo in the upper left corner.
Left side bar: “Circuits”
Button: “Create a new circuit”
Dropdown on right: change “Components - Basic” to “Starters - Arduino.
Select “Breadboard” and drag it out (may lag, go slow).
Change back to “Components - Basic”. Search for “potentiometer” if you can’t see it.
Here is an example with one light that repeats a cycle from off to dim to bright every 1.2 seconds.