Integrations I wrote years ago
Wow... I just realized from your latest email that you have an API. It looks fantastic! I've been wanting this for years! (I just recently got the new YNAB.)
With the old YNAB - version 2 or 3 actually, I had written some of my own tools to integrate with YNAB.
One tool, that I wrote in Ruby, would allow you to create a text file that lets you specify your own categories for reporting. And you can specify which budget categories should fall under that heading for the purposes of that report. Then you'd run a script and it would show you the total spending by month across those categories. This would allow you to essentially rearrange your categories any way you wanted, for summing in reports.
The other tool, that I wrote in Scala, would read through your email, pull out receipts, and generate transactions from them in a CSV file, that you could then import into YNAB. It required that you set up some filtering in (say Gmail) that would put the receipts into a single folder. It also was a bit fragile - sometimes receipt generators such as Square would change their format, and I'd have to fix the program. But in theory I could have made the process of building the matching a little easier.
I gave up on it because when you import transactions from CSVs, YNAB thinks they're bank transactions, so when you later import bank transactions, it won't reconcile them together. This whole tool isn't as useful in the new YNAB, because it does automatic import. But in theory you might get some better information out of the emails, or you could import them sooner.
Maybe I'll get around to building some integration with this API. I love APIs. I might write a Haskell library to connect with YNAB, since that's my language of choice at the moment.