Had some time to think about this and read through all the comments of this thread.
At least with my experience of these types of payments, they’re almost always online (iTunes, Amazon, etc), with the exception of paying for fuel at the pump.
Monzo currently have absolutely no way of knowing neither the value or the date the pending payment will be transacted.
I can’t see an ideal solution because the way card payments are made haven’t really changed since the introduction of cards decades ago, before the internet became accessible to the public.
The ideal solution would be for all payments to initiated via the API (the availability of which is on the roadmap here) and include additional data in the payload relating to the subsequent payment. It would only need to contain the amount and date the transaction will be attempted. They would then be able to automatically show in the feed without any need for manual entry.
I can’t see this becoming mainstream quickly after the launch of the feature and possibly never will. But because most of these type of payments are from online merchants as I say then PGP (Payment Gateway Providers) may gradually begin to support it. They would just need to recognise that the card is a Monzo card and initiate the payment via API instead of the conventional card number/expiration date/cvc method.
The only short-term solution I see is manual entry
I don’t think it would be necessary to search a big list of all merchants, instead only the merchants that have previously passed the active card check on your card. They may not always check for an active card before every payment, but they will have done previously at some point.