Hi @maddiemhc,
Thanks for sharing this question with our Klaviyo community. I am glad you asked this question and I’m happy to help provide clarity.
You’re absolutely correct on your first point, if a user fills out signup form A with $source X and then subsequently fills out signup form B with $source Y, the $source value will be updated from X to Y.
Assuming this user is already a part of the flow calling for $source X, this user would be skipped from subsequent emails because flow filters are evaluated before each email in the flow sends. Therefore, if the flow filter value calls for $source X and the $source is Y when the email is due to send, the user in the flow will be skipped. The same principle applies for conditional splits.
There are a couple of solutions. The first is to update the hidden property for the ebook signup form to another value. Instead of $source, for example, you can use $source1. You can adjust the $source value, (or any value for that matter) on the form by clicking on the Call to Action (CTA) button of the signup form. You may find this post helpful for a visual. From there, update the flow filter in your ebook flow to $source1. Net-new users filling out this form will log $source1 and will proceed through the flow as normal except, even if users fill out the other signup form after filling out the ebook signup, the $source1 value will not get overridden since it’s its own discrete property.
Another solution is to change the List to Submit of the form. The idea here is to send ebook folks down a flow triggered off of a separate list (exclusively for ebook subscribers) so $source is not needed at all. This solution involves first creating a net-new list. Next, clone the existing flow (removing any filters) and select the new-net list as the trigger. Turn all emails in the cloned flow to live mode. Turn all emails in the original flow to draft mode. Finally, change the list the ebook signup form submits to, to the newly-created list by clicking on the CTA button of the form under List to Submit. Now, anyone who fills out the ebook signup will join this new list and go through this new flow.
I hope that is helpful!