Today, I had another problem with CATIA, I wanted to lock toolbar position because each time when I opened a new toolbar from another, the position was changed or closed.
To fix the position of all toolbars, you should click on Tools -> Customize -> Options and check the option Lock Toolbar Position. I recommend to use this option only after you put all the command on toolbars because after that you will be not able to modify the positions of toolbars. All toolbars position will be frozen after you check this option.
In same panel, you have available also the Icon Size Ratio, the command that I use when I want to increase the size of the icons in CATIA. You can increase this size from 1 (standard) in 0.1 increments up to 5 (maximum). I recommend to use maximum 1 or 2 steps. This setting is very useful for people that use eyeglasses.