Hi @kate,
This is how I have been working to address categories/groups and to hopefully learn from others: Category & Groups
Here is the Google Sheet link
I have found in fairly short time that once I refined the categories and groups to my style and then using AutoCat to categorize and rename transactions that Tiller is far better than the other tools I have used.
Hope this feedback and suggestion helps!
P.S. I’d enjoy learning from what you export from Mint.