Being able to set dates as intervals on a timeline

In several cases in my projects I am needing to generate notifications for team members to do certain tasks at set intervals on a project, eg at the start, half-way through, and at the end of a project. automations, however, only allow for dates for notifications to be set on a specific due date, rather than being able to generate due dates based on timeline intervals.

It would be incredibly helpful to be able to set notification dates in automations based on intervals on timelines, or set intervals before and after a certain date.