NetBeans Java GUI Project - Design tab missing

I'm a total beginner in NetBeans, we have a project we need to modify with Drag&Drop, but the 'Design' tab doesnt show up for the java file in NetBeans.

How do I proceed?

The NetBeans GUI designer only works if a corresponding .form file is available.

If there is no such file, the "Design" tab won't be available.

Either that JFrame class wasn't created through the GUI designer or someone deleted the .form file. Looking at the partial code, I doubt the class was generated through the GUI designer in the first place. The GUI designer doesn't use static variables and it puts all those control creation statements at the end of the file, not the beginning.

In either case you must now make all changes manually in the Java code