According to the current documentation, runtime_fields cannot be of the data type range. Are there any plans or open issues or PRs to add this functionality? We have a lot of indices that contain two fields of type date which mark a start and a beginning, for visualisation purposes it would be very convenient to display the range between these dates.
I can't see anything in GitHub myself, might be worth making a feature request 
I've added Expand runtime_field data types to include ranges · Issue #139620 · elastic/kibana · GitHub, feel free to edit or assign the issue