If caramel sauce or mocha drizzle is already in the base build, "line the cup" will not charge. It's really there to help you not use the "ask me" button (since that doesn't account for inventory) and to make it easier to communicate when the customer wants their caramel or mocha to line the cup. If caramel drizzle or mocha drizzle is not in the base build, then there will be a charge. "Line the cup" also creates the standard across stores of 3 rings of drizzle at the top rim with the "extra" button now signaling on top only. Hope that helps!

I just wish they'd come up with some sort of modifier for "on the side" for cream and or sugars

I use line the cup if the customer as for drizzle all around. I use the extra button for when they specifically ask for extra caramel/mocha. I know those customers will not be happy with just 3 rings around.