I intended to refer to an underground belt that switched automatically from a (non-underground) transport belt.
If you have the transport belt on your cursor, you can't move the exit.

When a normal belt is dragged, the underground belts are placed at the shortest distance possible while avoiding obstacles.
However, I require an option to place them at the longest distance.
It would be preferable to switch this function by pressing the alt key or similar while dragging.