Years ago, I sync’d both the Monzo Personal account and the Monzo Joint account with YNAB thanks to @BritishLibrary’s amazing instructions on how to set up the (free) Monzo/Heroku/YNAB configuration. It was solid from set-up - BUT - I’ve since ditched YNAB and didn’t use it with VC’s. It worked for a Bills pot but only ‘one-way’ → a large transaction would leave the main account (when topping up the Bills pot), then amounts would be received into the main account followed closely by the Bill being paid. So you had visibility of the main account, but not the pot.
But like I said, once set-up properly, it was solid.
The Monzo API may be the sticking point - there’s limited access to pots and you get access to a total_balance figure which is the account balance plus the balance of all the pots under it. So it could be that individual pot transactions can’t be accessed.
I believe YNAB has now got things working with a Monzo Flex account, but pots are different.