Based on your screenshot you're using an MVC form.
If you choose the web framework to be Web forms only
when creating the form as shown in the screenshot screenshot
you'll be able to see the "Name for developers".
In Sitefinity 9.0 the Feather module is enabled by default and when creating forms Sitefinity creates by default MVC only forms.
Direct link to the documentation on : Types of forms: Web forms and MVC
More on working with MVC forms:
- Fields and elements of MVC forms
- Control the markup of MVC form fields
Do you want to have your say in the Sitefinity development roadmap? Do you want to know when a feature you requested is added or when a bug fixed? Explore the Telerik Sitefinity CMS Ideas&Feedback Portal
and vote to affect the priority of the items