A form key is a unique id of the corresponding form. With this key, you are able to determine which form has already been opened and/or submitted. The following article will explain where you can find this form key.
Step 1: Feedback Forms
In the left-hand panel, go to ‘Data collection’ > ‘Feedback forms’.
Step 2: Copy Form
Click on the icon with three dots of the feedback item you would like the form key of. Select ‘Copy form key’. The form key, a number and letter combination, is now copied to your clipboard.