Why would you want to allow your users to change the design of the layouts?
That seems an unusual design approach and possibly dangerous to the integrity of your database system.
It is just one form that the user may need to change some layout format. So about my question, is there a way that can enable the “Edit Layout” button or any other way that can edit a form layout?
You could open "Manage Database" by script, that let you add ( or rename ) a field...
But this seems very dangerous and the user couldn't positioning the field anywhere ( beside the default position ), because he can't go in Layout Mode.