With free BricsCad Shape! (function Quick draw) :)
Draw 2-3 volumes Make a Snapshot - dupplicate / rotate / resize the few volumes on a PNG transparent background Image and drag & drop the result on my own little tricky free prog https://editor.p5js.org/Pilou/full/y1GHaBqyT

Put it inside MagicaVoxel + File2Vox by Zarbuz et voilà! :)