It would be very nice if there would be a functionality for the tree to
load all its items (in case when using ajax to load them) when first
displaying the tree. Kind of recursive loading. This can be emulated right
now with a callback function for the onload event, which calls the
open_all() method, which in order loads all child items by opening the
parent item. This would be even nicer if there would be a way to do exactly
the same but without the visual feedback of loading animation for each node.

I was experimenting to hide the tree container element before calling the
open_all() method then redisplaying it, but it doesn't work when the tree
is hidden.