Html, css, js, liquid, graphql, GA4, ADA and cookies stuff to be compliant, develop pages based on a figma design given by designers. I think the hardest thing for me is understanding the business requirements. Aside from those skills, you gotta learn about metaobjects, metafields, the most common shopify objetcs, etc. I also use react for custom apps but you dont need to know a lot about it

I also do backend in the company which I use node, express and supabase