If you’re withdrawing cash for a single purpose, you can categorize it already. So you could of course withdraw several amounts separately & categorize each one differently, assuming that you’re going to spend multiples of £10 on something.
But obviously that’s time consuming and you might not know what you want to buy in advance so I’m guessing you’d like to have this feature
The last comment I can find from Hugo on this (quite a while ago) was
So this challenge + the £3k annual withdrawal limit are good reasons to try to avoid withdrawing cash whenever possible…