Thank you for your answers.
I am already using the equatools, and while they are certainly a good improvement, I still find that the tools are not very precise, you're never sure that you click on a line, for example. And to expand a line, it's just "gessing" until you get the line and its extension aligned.
Maybe I'm doing it wrong, but that's how I feel. Maybe with time I'll find some tricks to use them better.
I think that changing those tools is most likely not possible, but since I'm not a modder, I asked, to be sure.
As for the real nav, I am not at the point of using it at all
, but I will certainly have a look at your tutorial, trevally. Thanks for the heads up.