No I didn't figure out how to enter credit notes.
The only solution I found was to cancel my subscribtion and go else where.
I signed up for the Simple Start plan, which is advertised as "Making Tax Digital" ready.
But it couldn't handle basic things such as credit notes!
To process credit notes, you need to subscribe to £24 a month Essentials plan.
It's completely false advertising so I closed my account and got a refund.
