Add duration to a new task while creating it

When I create a new task, I can assign a set time, but not a duration. Therefore, if I want to customise the duration, I need to do a two step process. First, create the task, then edit it, rather than just assigning the duration  to the task directly during the creation process. Is this an oversight or by design? As you can assign almost everything else e.g. role/time/objective, when creating the task, it seems more like an oversight.