What are Study Extensions in COMSOL and how do I alter this?

I am currently trying to run an analysis with a stationary study on a cracked plate with a thermal load applied. I would like to modify the Study Extensions so that it runs twice for two studies where the thermal load is switched for the other study. I am not sure how to go about this due to my lack of experience using COMSOL, I would appreciate any advice given.

Thank you.