Short answer - yes, this can be done.
In 8.0, you can use the Preference Admin Create Preference UI for this. For 9.0, they left this out - you need to create using LoadFromFile (uggghhh). For 9.1, the Create UI is back.
There is a TAN on how to LoadFromFile in 9.0. It's incredibly confusing, and requires several non-intuitive steps. Recommendation - ask for a webex with Tech Support to lead you thru it.
Longer answer (and rant):
In my opinion, no real business can use Promotion as provided. As provided, all promotions all the creator to select whether approval is needed or not. So, the minimum configuration needed is to eliminate the Notify only option.
On top of this, you may want to use a different workflow process to promote to the same state depending on the context (Product or Library). To do this, you have to have a preference VALUE (not a new preference) in that context that overrides that created at Site and/or Org level.
We use either no workflow or a different workflow for every target state in our standard LC, and override with a different wf that includes additional approvals in several special Librares.
Promotion is one of the most important but least-well-documented elements of the system it seems.
