As I understand - you need a new vertex on edge exactly in the place where it intersects with another edge.
Here is it.
Warning: orange is a selection color in this examples.
Make a reference oblect:
Select edge that willl be cutted:
Cut it in half (create new vertex):
Click RMB & select "Intersect [RMB]"
Pick edge to set direction of new vertex movement & click RMB
Pick vertex to move & click RMB
Pick plane on the reference oblect (to which we will move vertex) & click RMB
Pick point on edge that intersects & click RMB
Done.
Here is it.
Warning: orange is a selection color in this examples.
Make a reference oblect:
Select edge that willl be cutted:
Cut it in half (create new vertex):
Click RMB & select "Intersect [RMB]"
Pick edge to set direction of new vertex movement & click RMB
Pick vertex to move & click RMB
Pick plane on the reference oblect (to which we will move vertex) & click RMB
Pick point on edge that intersects & click RMB
Done.