How to program Pulse Width Modulation on a Unipi Neuron S103

I'm new here and Node-RED is new for me. I installed Node-RED on a Unipi Neuron S103 (raspberry pi inside) and I want do dim an electrical heater. I want to send short pulses to a solid state relais. Writing it myself in JavaScript is to difficult. I think I have to copy a JSON file (=JavaScript) in a Node-RED "function"? Can somebody help to make a pulse width modulation? #general