Defpoint Lines / Construction Lines / No Plot lines

Is there any way we can have a line that does not plot? (noplot/defpoint lines) I'm trying to line up my viewports and I would like to keep those detail lines that I used for later changes.

Could anyone give me some ideas please?

reference lines or planes are your only option... and even then they'll print unless you have that selection unchecked in the print dialog (off by default)

I guess you are right. There were some discussions on this I found and only way to do it is to create an invisible line. You can only see them when you hoover over them. That makes me wonder if the invisible line happens to lie right on top of another line, that line will not print either right?

I guess invisible line isn't a solution either.