I think this is not possible from the settings in current version of the system.
I think this option is left for the developers - they now have API for manipulation with own action center items, so they may implement such behavior if it is appropriate.
This will come with time as more developers will made updates for their apps and start to manage their notifications in better ways for new system.
Other example would be multiple notifications about one particular event which is currently generating multiple notification items - myBattery and its 20%,19%,18%,17% (well,you get the point). In this case I care about only one item and that would be the last one. This is another task for developers as they can delete notification item if the new one should replace the old one.
Extract from WPCentral article on action center (the bold lines are relevant to your question):
- 20 Notifications per app
- Persistent notifications for 7 days (or shorter)
- Users can “chase” (tap) a notification
- Users can remove a notification
- Users can remove a group of notifications
- Users can remove all notifications
- Action Center is only available on phones
Action Center Management APIs
- Manage app notifications
- Developers can remove one or many notifications
- Developers can tag and group notifications
- Developers can replace a notification with a new one
- Developers can set an expiration on notifications
- Developers can send “Ghost Toast” notifications
And what is Ghost Toast?
An app can send you a notification without turning your display on or alerting you if it’s not that important. An example of that would be an update about gaining a new follower or friend request on a social network. It’s something you can attend to later and don’t need to divert your attention towards right away. It’ll still show up in the Action Center, but only when you purposefully go there.