Hello there Hugo,
Hope you're doing well.
To be honest, I don't think it is possible to change the name of the application using the Extensibility Configurations.
If you want to change the name from the OutSystems side, you will need to change the name directly in the application (in Service Studio).
If your objective is to control the name that appears in the stores and after installation, it also depends where you want to submit.
If you're going to submit it to the Google Play Store, they allow you to manage the name of your application in the developer console, so you can customize it.
If you're going to submit it to the App Store, unfortunately the name is strictly dependent of the IPA file, so you'll need to have the correct name by the time you are submitting the file. And you can only change the name of the application with a new submission of a new IPA file.
Hope that this helps you!
Kind regards,
Rui Barradas