Not OP, but there's not much to do about them - best way is to enter manually in the app at the time of purchase or write them down in a notebook and enter them in batch once in a couple days or per week.
If your cash spending is sufficiently small that you don't care much to tracking each cash transaction individually, you can just track money as a category instead of an account - just record an outflow transaction in your bank account when you withdraw.
I don't use ynab anymore, but when I did, I usually just didn't include cash in it. I almost never use cash, and so it made sense to just deduct the money when it became cash.
