anty21ro - I didn't see your .capx buy you can simply do this by making 2 (2x2) tiled backgrounds with, for example if the Los angle is 90 degrees then the 1st tiled background should be 45 degrees and the 2nd one should be -45 degrees.
In measuring the distance you can do this by trigonometric formulas or simply make a 3rd (2x2) tiledbackground in the middle with 0 degrees and the width/height is your distance.
This is a method for accurately checking the los range and angle. But yeah, I agree this feature premade in the editor with an option would be great also.
Sorry if it isn't clear and I couldn't give you any samples since I'm only using my phone.