Short answer: It automatically syncs to your “most open” service. It cannot be manually changed right now.
Your profile status automatically changes based on your service statuses - it defaults to the "most open" service. The order goes: OPEN > WAITLIST > CLOSED > HIDDEN.
This means if you have all WAITLIST services except 1 OPEN, your entire profile will be "open". If you want your status to become WAITLIST, all your services must either be WAITLIST, CLOSED, or HIDDEN.