Could you add this feature, when 2 points selected, add a feature to calculate the slop between these 2 points. So we can see how steep a slop is in this section. Result should be given in angle between the slop and earth surface.
I think I know what you mean, but this would apply to a _range_ of points, not between any 2 points. And then imagine that your track winds round and round a hill - do you want to know the angle from the first point to the last point, or the gradient of the road (which will be much flatter than a direct line)?
If you want the average gradient, you can already work this out pretty easily - just take the altitude difference from the range details panel and divide by the total distance covered. But obviously this is not the angle to the earth surface(!).
I think the gradient of a tracksegment is sometimes very helpful.
Prune already shows the velocity between two trackpoints.
Perhaps you can add here the gradient between two trackpoints. Divide the difference in altitude by the horizontal distance. The result should be shown as percentage.
The same should work for a range of points. (using the total distance, not the direct line)