I built this old fashioned way: with a tape measure and a pencil. Well, OK a couple of tape measures and "Hey! Where the hell did that pencil go now?"
The loft along the back wall has been there for years. Everything else was designed and built today, on the fly. The only "computer" involved was my phone playing a whole lot of Allman Brothers, Stevie Ray Vaughan and similar artists on a Bluetooth speaker. ;-)
There a single piece of wood that serves no actual purpose. It was added for purely aesthetic reasons.
(It's not the short 2x4 on the upper right. That will be used to hang seasonal yard equipment, e.g. brooms or snow shovels. I'll probably finish off all the ends of the shelves in that section. It'll look more solid/finished.)
OK, so where's unnecessary piece of "structure"?