How to generate form pre-fill data with URL - Field type "Quick Select"

Hi !

Following the instructions detailed in this guide (HELP: Advanced Form Features / Form Prefill, I have been able to create my custom URL to open a form with some of the fields pre-filled with what ever I need.

However, I’m struggling to prefill a field type “Quick select”.

If this field ID is MyQuickSelect, and it has the 2 following options (opt1, opt2, opt3), how do I built the URL to prefill with opt2 selected for instance ?

I’ve tried prefill_MyQuickSelect=opt2, it doesn’t work.
I’ve tried prefill_MyQuickSelect_opt2=true, it doesn’t work.

no clue how to do it…

ANy help would be much appreciated.

Thanks!