Splitting a payment across categories

A lot of the time, I will buy multiple things for different reasons in the same transaction. For example, the other day I went to Waterstone’s and bought a book for me, a card and a gift for a friend, and some stationery. I wish there was a way I could split up this transaction into different categories in my spending, as right now it’s all in the Shopping category at a glance it looks like I’ve spent all the money as a treat for myself - which isn’t great for budgeting!
Obviously I don’t want to complicate the UI too much, but it would be a great thing to consider looking into!

c.f. some of the ideas in

This feature has already been suggested. You can vote for it here: