Thank you for coming to the Community for help, @ljstrangpartners.

Adding bills using a mobile app in QuickBooks Online is currently unavailable. At this time, you can only use the Expense feature to record the bills in the mobile app. 

To do this task, you can use the web version of QBO. Simply open a browser like Google Chrome, Internet Explorer, or Mozilla Firefox and log in to your QBO account. For detailed steps, see the Enter bills section through this article: How to enter and pay bills.

Mobile app features differ from one kind of phone model to another. You can open this article to see which model has which feature available: Compare mobile app features.

Please feel free to drop your questions below. I'll make sure to get back to you. Have a good day!