I have just deleted Python and my two copies of Inkscape, so I could do a fresh install of Inkscape 0.92 and include the tabbed boxmaker extension. After a lot of faffing about due to the confused situation of the two Inkscape versions - it all works beautifully.
Attachment 23690 and you can save as a DXF as well !
After struggling with AutoCAD (and giving up !), this is neat.