I'm also having this issue. If I have something of a certain width in mm or inches in Designer, it imports in other programs at a different size. This is a huge issue when I'm trying to get accurate cuts on a laser. To get close, I'm just doing what one of the people above alluded to. E.g., I have a design that's 20 inches wide. Everything else (Inkscape, Lighburn) imports it as 15 inches wide. 15/20 = 0.75. 72dpi/0.75 = 96dpi. So when I export from Designer I have to change it from 72 to 96 dpi. This seemed to get me close to the right number (it's a couple decimal places off still when I import).
