Discount per client/customer

Is there a way to have an automatic discount per customer?
That is to have a client custom field with a default discount (that’s the easy part) that appears automatically in the invoice Discount field?
I need to set a [different] default discount (usually percentage) to most clients (think resellers) and I’d want this discount to appear automatically in the Discount field when creating a new invoice.
How do I do that?

Sorry, it isn’t supported

That’s right, it isn’t supported out of the box. I was thinkimng maybe someone can point me to what fields in which files need to be addressed. Forgot to say it’s for a self hosted IN.

Do you want to implement the change in the web app (PHP/Laravel) or the mobile app (Dart/Flutter).

In the web app.

Ha, I was just having a look at knockout.blade.php and the next on the grep list was edit.blade.php :)))
Thank you.