If this is the best way to do this, then I can create the garage with a separate file and 'copy and paste' it into the existing file (where it would fit on the parcel). The issue I am having is not in 'copying and pasting the garage' into the file but 'coping and pasting' the garage so it shows up with the correct height, floor, roofing, and foundation, and other dimensions in line with the lot, so that it looks normal on the lot.
The garage floor base is lower than the house floor base and after doing what you are suggesting, I have found that the garage I 'copy and pasted' (note I have attempted the copy to the 1st floor and the basement floor of the existing structure multiple times) had a second floor created somehow, so the garage looks more like a 1.75 story garage vs. 1.0 story garage, given the desired garage roof pitch is 6:12. I have spent countless hours attempting to modify the stem wall heights and cannot get this figured out.
Sorry if this sounds confusing, however I have not better way to articulate the challenge.
MC