So sending money works great. I love that you can choose a category too. But often it is for fuel and something else, fuel & shopping. The only way you can put these things into the right categories is to do multiple sends of money. What would be great is if you can send the money with the categories selected and once the money is sent, to be able then to type in which category you sent a certain amount of money for. It would really help keep a much more accurate record of what money is being spent on while making it quick to do so and not having to make multiple transactions to make sure everything is accounted for.
This is serious organisation at work!
Have you considered using hashtags within these transactions, so you can search for each type - hash tag the payment and add notes for how the sum was split.
Granted, this wouldn’t reflect in the summary tab, but think would give you a workaround until Monzo get to a point of being able to do split category transactions?
Wish I was so organised with my budget!