To add a "cancel" function to a button, do I need to create a client script and link to my suitelet?

Yeah add the button and have it call whatever your cancel is going to do. You'll need a client script for this.

thanks @creece

Typically you can just window.location = window.location and let the page refresh unless you have some parameters in the URL and in that case, you can resolve the suitelet and just do window.location = suitelet url

Interesting. Thanks. I will see more about this. Thank you very much @creece