Do you need to modify a curve? To control its tangency and control points?
Like this?

You only have to activate a visualization for that specific curve. On the left panel, click on this icon, which will activate the command PointsOn.

 

Disclaimer: this is a fast guide, a tutorial, an how-to article that I personally wrote for you. Feel free to write here any kind of suggestion! It is helpful if you need to solve your problem, if you need a tip or if you are in trouble and you need an help!