Heyy 
Just a quick update here 
our ClickFunnels plugins have been deprecated, so this workaround is no longer maintained.
If you’re looking to migrate your funnel into Funnelish, you can contact our support team and they can guide you through the process.
And if your goal is to achieve multi-product selection on upsells inside Funnelish, you can now do this natively, no hacks or plugins needed.
Check out this article for how it works: How to Allow Multiple Product Selection on Funnelish Upsells
If you need any help with the setup or migration, feel free to reach out!