I'm also wondering, what is it? have you found anything?

No, sorry... Don't know what it's good for. So I gave up researching

Parent mode makes it so that the map on the interface doesn't change when clicking on a linked zone. This allows you to create a 'parent zone' (possibly a larger map of an area) with 'children' created by adding links to it (like smaller, zoomed in areas of the larger map), and you'll be able to switch between the smaller 'child' zones much quicker, because you won't have to completely transition back to the main zone every time. Hope this helps, even though I'm answering well over a year late :P