Custom Form Builder part

Is there a way to customize the Form Builder part?
I would like to make a part with some custom features, like an input for a TextLine, and some custom css classes for the divs, using the Form Builder controller and its features. Do you know a way to do that?

Form Builder application: https://market.enonic.com/vendors/enonic/form-builder

Sure, just use the project as a starter and build your own version of the app.