Click OK and open your target page in the editor, you'll now see the Scaffolding option among the edit modes:
You may notice that the documentation for Scaffolding is present but limited for AEM 6.5, but the entries in the Classic UI Tools menu are marked as "(Deprecated)":
I'm not sure what the official position of Adobe is on the subject (maybe someone can tell us if they have more info), but you could consider using Content Fragments and Dynamic Templates instead, two features that are going strong in AEM 6.5.
Basically the idea would be to create a template that allows one Image and one Content Fragment component for example. Then create a Content Fragment Model which would allow users to create new Content Fragments using a simple form-based interface. They would just need to point the Content Fragment component to their Content Fragment I'm not sure exactly what your requirement is so it's just a suggestion of course.