To get the shortest route you can imagine plotting a course in a 3-dimensional matrix. Just imagine to make a route from a to b in a 3-axis cartesian coordinate system.
You note the two coordinates, visible from the star map. Then you can divide the distance by your jumprange (e.g. 140 / 20) and change coordinates by the according value. Then you get the coordinates of your target position for each stop and can look around there for stars.
calc looks a bit like that
View attachment 3627
The problem however, is, that while you find a rather direct route with only few jumps, they take waywayway more fuel. So going a shorter route but having a few more shorter jumps is actually the way to go, unless you can jump the short route in one go.
EDIT: This way I ended up with a route like this:
View attachment 3628
but it is sheit.
1. Too much fuel use.
2. have to go to galaxy map for most jumps due to navigation window only showing up until around 15 Ly and then maxing out because lots of stars
Having custom routes and star targets for the navigation window would help A LOT here.