Horizontal markers on the Navbal.

[Tw1]

We've got the heading indicator, which is pretty useful, but having some horizontal marks on the Navball could be useful:

These could help you see if your prograde marker, and therefore your orbit are ending up in the right inclination when attempting to launch into the right plane from the ground.

This would be especially useful if axial tilts are added someday, and Kerbin is given a tiny (3-5°) inclination.

Ideally, they'd be a lot fainter than in this picture.

[Kasuha]

Besides heading indicator showing me which way I am pointing, it would be nice to have another heading value telling me which direction I am moving. Relative to the selected frame (surface/orbit). But neither tells me the inclination of my current trajectory and I'm pretty certain that the horizontal marker would not tell you that either. I am not even sure if there is a way to display your orbital inclination on navball in a non-confusing manner. You may be heading and flying straight to the east while your inclination is 60 degrees - it all depends on your geographic position. Personally I'd just add a small side display telling you the most important numbers - Ap, Pe, and inclination.