qt:object properties can be accessed with qt:property (setf-able). The name of the property can be either a string in C++ style or a symbol in Lisp style. The predefined Qt properties can be accessed with symbols in the keyword package.

(let ((object (make-instance 'qt:object)))
  (setf (qt:property object :object-name) "Foo")
  (assert (string= "Foo" (qt:property object "objectName"))))