Using parent tasks to hold whole sections of a project, it would be very useful to be able to use the Filter to specifically see the sub- tasks from a particular parent task (and all sub layers depending on how many there are in the workspace)

I'm using custom fields as a workaround, but the amount of times that users have not assigned the correct one or there is none assigned at all has me writing this feature request. Because this kind of functionality would solve this issue.