At the "Thank You" block, you'll find the optional setting "Survey exit link (only for 3rd-party panels)", where you can fill in the exit link.

Currently, we're supporting exit links with the format:
​

OR
​

OR

OR in any combination

whereas {value}, $value, {{{value}}} are placeholders for the key.

This way, you can catch and send back certain variables (value, etc.) to your panel partner and track the associated responses on the results page.