I think the trick offered by @Henry16 is no longer possible because i think not possible to open a "Pricing Settings" sidebar inside calendar and also impossible to turn smart pricing on and off "real quick". Once you turn it on, it will put you through a bunch of confirmations to talk you out of turning it off.
Today Airbnb support told me there is no reset button. Once you set a custom price in the calendar, those dates become disengaged from base pricing. You have to remember those dates will not change with base price. you have to change them manually from now until eternity, unless you call in and ask Airbnb to reset your pricing. I did that today.
Multi-billion dollar company and has no reset button. Go figure.
If you know a trick that currently works, please post.