Hi brian-corecontra,
Congrats on your first post in the Community. It's essential you're able to import and manage Sales Receipts in QuickBooks and I'll be glad to share more info.
It's good you've imported your custom Sales Receipts using the web-browser. While this function isn't available on the mobile version, you can still access and use your imported custom templates in the mobile version. In case you're not seeing custom templates in the mobile version, I troubleshooting the mobile app by uninstalling the app and reinstalling it. I also suggest making sure that the custom template in question is also showing on the web-browser.
Give this a try and let me know how you make out. I'll be one message away in case you have other questions.