As far as I know it is not possible to switch it on.
You might find function
DESCENDANTS (http://docs.intersystems.com/latest/csp/docbook/DocBook.UI.Page.cls?KEY=...) helpful.
For time dimension, all members of the level are generated and available to queries that show empty. This means
SELECT DESCENDANTS([DateOfSale].[YearSold].&,DateOfSale.DaySold) ON 1 FROM HoleFoods
will show all days from 2015 on rows, whether there are facts recorded for those days or not.