I'm sorry for the huge delay asked for this question, but it appears, that this dialog layout is hardcoded in the default Cinema 4D layout, so when you open it this dialog, it loads this layout by default since it's saved in the default Cinema 4D layout.
Unfortunately, there is no way to do the same thing with code but you can split your GUI in 2 parts and let the user build its own layout with all the Command and your Dialog bellow.
Cheers,
Maxime.