Step 1: Remove the product(s) from your campaign.
Step 2: Click "Refresh data", and the app will calculate the normal prices. This might take a moment depending on the amount of variants, so please be patient.
All set! The previous campaign price is now your new Omnibus price.
Optional: If you want to start a new campaign, place the desired product(s) in the campaign after the calculation from step 2 is ready.