How can I customize the duplicate entry error message in AppSheet?

[Emilio_arg]

Hi everyone,

I'm Emilio from Argentina, and I'm currently building my first apps using AppSheet. I'm really enjoying the platform so far.

I'm working on an app to manage user-role assignments, and I’ve run into a small issue. When a user tries to add a record that already exists (for example, the same user-role combination), they get this system message:

"There is already a record with key 'US00002 : ROL00002'

This message is too technical and not clear for regular users. I’d like to replace it with something more user-friendly, like:

"This user already has that role assigned."

Where can I configure a custom validation message like this?
I’m using Google Sheets as the backend, and the table is calle "rolPorUsuario"

Thanks in advance. I'm happy to be joining the AppSheet community.