I need to position an “Positioned Box” near the upper right corner and try to drag the box to the position, but whenever I come to close to the border, the box automatically snaps the nearest border.
Other software allows to hold SHIFT AND/OR CTRL down to disable the auto-snap mechanism.
I think what you are looking for is the SHIFT+ARROW KEY combination. If you drag a box with your mouse and come close to a border it snaps to the border. If you use the SHIFT+ARROW KEY combination however, it will just move .0105 inches to the direction you want.
If you want perfect accuracy, you have to adjust the position in the Attributes panel.
Personally, I use mouse dragging to get it go a general area, then refine with the SHIFT+ARROW and use the Attributes to get a nice rounded number which is closest to the position I want, for instance change the Y-position from 1.2317 to 1.2300.
EDIT: You have to click on the border of the box first, not inside the box.