Ideal Racing Line and tarmac

I really like netkar and there are a lot of addon-tracks but the most tracks have (in my opinion) one or two big problems:

1. there is no ideal racing line
2. Some of the tracks are only grey, I can't see the structure of the track.

For example, the SPA 2010 Layout:
https://www.youtube.com/watch?v=3Vkg0xyZSJ4

And an older Version of Spa:
https://www.youtube.com/watch?v=uBwl-QlhIaE

Here another example, Crema RSR (left) and Crema original (right):
https://2img.net/r/ihimg/f/837/nkscrformulaks2cremarsr.jpg/

Is it possible to fix this or do I have to change a setting?

thats simply down to the author of the track. id say only 50% of custom tracks have a darker racing line, meaning you have to find the correct line yourself:

https://www.youtube.com/watch?v=U-hCYTAGNfM

theres nothing you can do. some tracks have it and some dont - it depends how much effort the creator has put in.

It might also have something to do with track formats. Spa 2010 is the newer .kto, 2001 the older .nko. Same with Crema RSR (kto) & the original Crema (nko). Then again it could have nothing to do with it, but I think under an old ver. of nKPro (1.03) skid marks were generated automatically.

Marius is right. That functionality isn't available anymore. It's not possible anymore to add the skid marks on the track. No matter if it's on the nko or kto. It's not loading anymore the groove.txt