You cannot change the display name of the "Form name" displayed on the dashboard form.
Dashboard form view screen
The 'Form name' is the same as the 'Form name' specified in the Design Editor. It cannot be changed in the dashboard.
Form name setting screen in Design Editor
If you change the "Form name" in the Design Editor, the "Form name" displayed on the dashboard will also change, but it will only apply to messages posted after the "Form name" is changed. The Form name of the messages posted before the Form name was changed will not be changed as it was before the change.