You can run hourly with supervisor rules, or on a schedule with a scheduled workflow. 

What are you trying to achieve by Doing something every 15 minutes?

I can’t remember what it was for, it was something I thought of last night and wondered if it could be done.

Hello! Good day. Thanks for reaching out to us on community.

Regarding your query, in Freshservice, event-based workflows can only be triggered by specific events, and scheduled workflows currently allow scheduling on a daily, weekly, or monthly basis. Running a workflow every 15 minutes or hour is not natively supported within Freshservice. However, a workaround can be implemented by using external tools like a custom script or a third-party scheduler (e.g., cron jobs) that calls the Freshservice API periodically (every 15 minutes or hour) to check for specific conditions and trigger actions accordingly.