A feature that I'm adding to Marvin is that, if you know the URL scheme for a dictionary app, you'll be able to create a custom "tap and hold" menu button in Marvin to take you to the definition of the selected text to a dictionary app of your choice. I'm still waiting for a reply from Abbyy regarding whether they have a URL scheme for Lingvo. If the Collins dictionary has one such as scheme, you'd be able to add a custom button in Marvin for it too.
Regarding the library sort bug, that is the way I had made it (it is by design). However, now that you mention it, I realise it was a lazy and somewhat stupid choice. I've already fixed Marvin to remember your last chosen sort order and default to it.