For nearly two years, I've been running
Service Scrubber after each OmniOutliner Pro upgrade to eliminate the Service > OmniOutliner: Add to clippings keyboard shortcut.
I'm finally getting around to making a formal request for OmniOutliner to offer a user preference to customize (or eliminate) this conflicting keyboard shortcut.
I'm sorry, SearchGoogle got there first, and I can't retrain these old fingers.
[submitted as formal feedback]