Add internal drawers behind wardrobe shutters
Add drawers on a partition and switch the new Drawer System's Properties > Type to Internal so the drawers sit behind the shutters.
In a wardrobe, 'Add drawers' on a partition adds external drawers: the new Drawer System's Properties > Type (Construction tab, also on Quick Access) reads External.
Switch the new Drawer System's Properties > Type to Internal there for drawers behind the shutters.
The new Drawer System's Properties hold Construction Type (Normal or Box Type) and Drawer Depth Reduction.