Center mode
The center mode requires you to draw in two ways, depending on the selected class.
Machine-assisted box
Select a class
Place a point at the front or back (center) of the object
Place another point at the opposite side of the object to set the length
A cuboid should appear

Manual box
Select a class
Place a point at the front or back (center) of the object
Place another point on the opposite side to set the length
If you regret where you placed the second point, you can press Shift, and the red arrow will appear again
Move the cursor to the side and click when you feel happy with the width
A cuboid should appear.

If you wish to draw a manual box instead of with automation - press shift while following the steps above.
Drag the arrow across the longest side of the object. Dragging the arrow across the shorter side of the object will produce a small 3D box that doesn't include all points.
Objects that are considered static do not move throughout the sequence. Use the traffic light button to find and mark frames where static objects are not visible.