No, there is no way to modify the 'design' body from within the simplified mode.
You could try just suppressing rounds and holes in the design mode, but you might get unexpected results.
This is where a mixture of sync and ordered could help, as you can do your 'shape' definition modelling in sync, with your rounds and holes in ordered. That might help, but I can't say for certain as I don't really us sync that much.
HP Z420 16GB RAM Quadro K4000 ST10 MP3 on Windows 10 Pro 64.