Create two rectangles and use convert to path command
Use edit nodes command to select all of the nodes from one of the rectangles
Snap the selected rectangle adjacent to the other rectangle
use Alt-D command to remove the duplicate lines between the rectangles
LightBurn message shows no Duplicates found, but duplicate lines do exist between the two rectangles and therefore the laser cuts the duplicate lines
It would be nice if LightBurn software would automatically insert a node at the intersection where two lines cross