How can I use the "System" section with the OpenAI API?

I’m referring to the section on the left when you press “Chat”

Are you able to influence it programmatically or is it only available in the website?

Good question, from the playground you can only add one system message, it can be used for initial instructions.

From the api you can add multiple system messages even in between but the effectiveness of doing that is unknown.

It is described in API.