I’ve figured out a solution for this if you’re still looking.
The concept is that when the form is submitted, we use Jquery to click a hidden button which has the action URL placed instead.
So, for example, we have a normal form with no action URL set. This should submit as normal and send the form data to the forms section in Settings.
Add an HTML embed to the form with code that looks like the following:
<button type="submit" id="hidden-button" onclick="window.open('https://your-url-here.com')">Submit</button>
We then set the HTML embed to display:none so that it isn’t visible to visitors on the page.
In your site’s Footer Code, you then add the following script:
You’ll need to switch ‘.notification-form’ with your form’s class, and ‘#hidden-button’ with the ID of the button you’ve added in to the HTML embed.
Now, then the form is successfully submitted, it clicks the hidden button which opens up your URL in a new tab.
Hopefully that helps!