There is quite a bit of missing or incorrect information about grouping objects or making architectural blocks on this and other sites.  Firstly:  the "make architectural block" icon or symbol (which no posts seem to mention) is a graphic of a 3D perspective of a "cube" which appears in the lower left tool bar (at least on my version - Home Designer Pro 2021).and does NOT appear under the EDIT tab on the main menu as some tips suggest.  Secondly:  it does NOT appear, and is apparently NOT functional, if you select CAD objects such as a square or a circle.  Nor does is appear if you select windows, doors, or walls.  Thirdly:  simply copying & pasting multiple CAD objects, windows, doors, & walls does work using the regular copy and past procedure.