Please clarify, are you referring to a reminder that will recur every 3 hours or one that will go off 3 hours before the task's deadline?
In the first case, you would have to set multiple reminders, each recurring every day on a different hour, for example:
- every day at 7:00
- every day at 10:00
- every day at 13:00
...and so on.
In the second case, you can set a specific due time within the task's date, such as "every day at 18:00", right-click on a task with such date (or use the clock icon while adding it) and choose a relative reminder set to "3 hours before".
Every three hours
Thank you for clarifying. That's unfortunately not possible right now so the first workaround would be the best option for now. We will consider adding more date formats in the future, though.