For now there's a URL parameter libs that takes a semicolon separated list of the library sets you want, e.g.:
That's also the list of all possible values currently for that parameter. You've made me realise there's a bug with ER, BPMN and iOS sets regarding this, we'll look at that.
We have discussed this and intend to persist the library settings between uses. A question for you, would you prefer this to be stored per browser (i.e. cookies) or per Google account (as a meta file in your Drive)?