is it possible to create a custom substate in each route like the error/loading substates?
It’s coming in Ember 1.11, it’s in the beta right now: http://emberjs.com/blog/2015/02/07/ember-1-10-0-released.html (almost at the bottom, named substates).
You also have to explicitly add the loading route to your routes
but I think that’s a bug.
Edit: If you mean another type of substate, I really don’t know. There’s an
intermediateTransitionTo() method on the router, maybe that’ll help.