How can I append the email address from a Wordpress Keap Official Opt-in From plugin to the success url?

I am trying to use Countdown Hero for a tripwire deadline funnel.

I can get the timer to work using a webhook in a sequence, but I can not get the Thank You page trigger to work because the Opt-in Form plugin does not append the submission’s email address to the thank you page redirect.

Can anyone help me figure out how to append the email from the WordPress plugin?