When you change the status of a child asset, it will ask “Downtime Type” (planned or unplanned). It will ask “Offline Since” where you can choose “Now”, “An Hour Ago”, “Yesterday”, “Last Week”, or you can choose a date. When you hit next, It will give you the option to choose the parent as well as other child assets. If you choose the parent it will take all the child assets offline as well. This will then show the whole hierarchy as offline.

Hope this helps.