Thanks for your reply, Brad. There's one additional thing I've observed (and please bear with me, because I have ZERO knowledge about software programming, so what I'm about to say may sound really stupid ).
This problem is definitely not related to closing and opening the LaunchBox program per se, but to the resizing of the program's window (i.e., 'unmaximizing' it when it's maximized and then maximizing it again).The thing is that, each time I close LaunchBox, the program window first unmaximizes for a split second before actually closing, which is why next time I launch the program, the "Details" section resets its width. Conversely, if, for instance, I change some settings under Options and tell LaunchBox to restart, it restarts without resizing the window first, and upon restarting, the Details section keeps the desired width.
So I guess what I'm saying is, I understand this may be a Windows bug, but is it necessary for the LaunchBox window to resize / unmaximize each time the program closes? Because I believe that's causing the issue and maybe it can be bypassed.