[Cottser]

With Quick Entry open, hit Control + Return to add a new item below or Shift + Return to add a new item above the current item.

You can also change Quick Entry so that Return doesn't save and exit by changing the preference under General that says "Return should also save and exit", in which case you would save and exit by hitting ⌘+S.

Personally, I use the first method, but of course it's up to you. Hope that helps.