I think he means, with the windows opening thing, that sometimes, usually when selecting vehicle replacements, you open your lines manager, it opens in the middle of the screen, and takes up most of .
Then you click replace, it opens up a new window, above it, taking up more screen, then you click compose vehicle, and then that windows opens in the bottom right, almost entirely off the screen.
I thin I would prefer the windows to just open above the last one in most cases.
Keep in mind, that I use the latest build 6219, and play in a fairly low resolution laptop screen (1366×768)
It doesn’t happen so much on a full HD screen.