Scripting "On user input" for Subforms and a Bug

Scripting "On user input" for Subforms and a Bug

My subform contains a dropdown field. I want a textbox in the subform's same row to display a value depending on what the user selects in the dropdown.

Clearly the "on add row" is not where to put this code. So I selected "configure filed actions" from the form builder:


And it loads a page that is totally not editable. If I hit the "free-flow scripting" button, nothing happens.


I did note the url for this strange page is:
creator.zoho.com/appbuilder/sigroup/lab-audit/form/Audit_Form/Audit_Findings/workflow/edit#OnUserInput

While the "on add row" is the same, and shows my code:
creator.zoho.com/appbuilder/sigroup/lab-audit/form/Audit_Form/Audit_Findings/workflow/edit#OnUserInput

So there's a misconfiguration on your side. And I need you to answer my original question.