Thanks for posting here today, @dhorneman.
I have some information about mileage notifications. Currently, the option to set up trip notifications is unavailable. You'll have to categorize them every time you record them in QuickBooks.
I can see how your idea would help us provide a more customer-friendly product interface. I recommend sending a product suggestion to our Product Developer. Here's the link: Customer Feedback for QuickBooks Online.
I'm also attaching this link to help you manage QuickBooks Self-Employed (QBSE)-related tasks. Feel free to browse this page: View all help in QBSE.
Feel free to let me know if you still have questions or concerns with mileage notifications. I'll be around to help. Take care and have a great day ahead.