Hello!

First off, you cannot lose contacts by upgrading Trombinoscope Contacts. Why? Because the extension uses data stored by the Contacts component, packaged with Joomla. So, you should be able to see the contacts under the Contacts component.

Secondly, the messages you are getting are 'deprecation' messages, not error. It's just a warning telling you that the way some functions are used will not work in the next major version of PHP (here PHP 9.0). So I suspect you are using a version of PHP > 8.1, that is why you are getting those messages. That should not affect your site and those messages should disappear once you limit error reporting in the global configuration of your site.

Note that I am in the process of removing those messages from my extensions and Joomla has also been working on eradicating them in v4.3.

Oh, I understand what you mean!

Unfortunately, adding a shortcut to the contact page inside the Trombinoscope menu is no longer possible in Joomla 4 because of the way the menu is built.