This thread is resolved. Here is a description of the problem and solution.
Problem: Currently, for site visitors where a language doesn't exist, English is shown as this is the default language. This works well for us. However, one exception is Brazilian Portuguese and Portuguese. Our site is translated into Brazilian Portuguese - whilst not ideal, we'd want visitors to see the Brazilian Portuguese version if the language code is set to (European) Portuguese.
Solution: I'm afraid that WPML doesn't have an option to do something like this. As you said, you should create add the Portuguese language. Only this way, the visitors will be redirected to it. To make things work the way you described - English Portuguese be redirected to Brazilian Portuguese, some custom coding is required.
This is the technical support forum for WPML - the multilingual WordPress plugin.
Everyone can read, but only WPML clients can post here. WPML team is replying on the forum 6 days per week, 22 hours per day.
No supporters are available to work today on this forum. Feel free to create tickets and we will handle it as soon as we are online. Thank you for your understanding.