I'm here to provide some troubleshooting steps to help you add more favorite mileage locations.
As I've tried replicating it on my end, I was able to add more than five favorite locations using the mileage tool. There are instances that this unusual behavior happens when saving your favorite mileage addresses.
Here are some possible reasons why:
The app version is not compatible with the mobile's operating system.
The app is piled up with a cache.
There is a connection issue between the app and the server.
With this, I'd suggest checking your mobile device's operating system if this is compatible with the QuickBooks Self-Employed (QBSE) app. Also, you'll want to update your QBSE app to refresh its stored cache data.
Here's how:
Open the Google Play store on your mobile device.
Select the Menu ☰ icon.
Click My apps & games.
In the Updates tab, find and select the QuickBooks Self-Employed app. Note: if you didn't see the QuickBooks Self-Employed app in the Updates tab, your app is already up to date.
Select Update.
If the issue persists, I'd recommend clearing the application's stored cache files from your mobile settings.
For future reference, you can check out these articles that contain steps on how to fix them: