There are 2 ways of doing this (..even though I believe this to be sort of a bug from Kunos SDK Editor).
1/ the simple but painful way
Load your track into the editor, load the AI line, and then go to AI tab; you can then manually (this is the painful part) move the markers by clicking on the <> arrows.
2/ a more intelligent (albeit longer) way, courtesy to
@LilSKi and
@Lucas L :
Lilski:
So I have a HUGE breakthrough for BLENDER users thanks to lucas-Xtremepsionic when it comes to the AI line INSIDE the editor. Since the beginning it has been impossible to precisely select parts of the AI line from within the editor. You get this: I clicked where the red arrow is and it selected where I circled. This makes it damn hard to edit the line.
Lucas found the answer in desperation when dealing with his huge Lake Louise.
Here is the process of making it work properly. What I did was I made a duplicate of my land and road object and sent to another layer in blender. You will be using this model only for editing the AI line.
Here is my duplicate model and you will notice its location is not 0,0,0. So the first step is to apply location
After you apply location the transform panel will look like this
Now the second step is you rotate the model on the X axis -90
Third step is to apply the rotation which will set everything back to 0 again
Now we need to export to the fbx. These are the settings for it. The key is Y forward and Z up. (Under normal conditions we use -Z forward and Y up)
I exported to a special AI.FBX as it will only be used for this purpose. I load into the editor as normal and load your recorded AI line. Now when you click the line it will actually select the line where you actually clicked.
Now you can use this video to fine tune your AI line the way it is supposed to work.