Hello Santi

Thank you for your purchase.

I am sorry to disappoint you, but unfortunately something like this is not possible with the plugin's built-in features.

You can only connect them manually, there's no automated process for that.

Hi again Santi

Well, you didn't ask about automatic creation of the customer, but automatic connection

If you enable this slider, every new customer will be created in Amelia's Customers section, and an "Amelia Customer" WordPress user will be created in WordPress' Users section. The customer in Amelia will automatically be linked to the WP user.

For existing customers, you can't automatically connect them, but you need to do it manually.

Hi again Santi

Nothing, really.

When a user clicks on that URL, the appointment should be canceled, and the user redirected to either the home page, or booking page.

You can create a couple of new pages, like "Successful cancellation" and "Unsuccessful cancellation", add content that would inform the user that they cancelled the service, or they haven't been able to do that (depending on the page), then paste those URLs in Amelia Settings/Notification Settings: