The easiest DIY solution to this is to go to your Vendors and go down to their Mailing Address.  Enter a "blank line" above their Name so that it lowers the entire Mailing Address one line and has a blank line now for the top line.

It is a bit time consuming and pretty stupid for a fix that an IT guy at QB could probably fix in a few minutes.  But its a heck of a lot better than taping or hunting down weird shaped window envelopes.