Can someone help me? I have a lead form on my website asking for a name and email. I would like to have AC to open an URL in a new window after the user submits the form. In the AC settings, I can only specify the URL (or thank you message), not any specifics. Having both the thank you message and the URL would be even better 
No, sorry. I reached out to support for this and this was the answer:
Currently, we don’t have a built-in option fin our platform to open a new tab/window when a contact clicks on the submit button on the form. The system will always redirect the contact to the url on the same tab/window.
As a workaround, the only option to have the form redirect to a new tab will be to add the form code to your website and makes changes to the full embed code to redirect to a new tab/window. This would require some custom coding, which is unfortunately out of my scope to advise on.
I will be redesigning my forms so they send the user to a new url in a new window.