Add functionality to delete references used in an NC step by RMB step in model tree. See images.

I might be wrong, but I think the way to remove curves that have been used for a trajectory such as this, you need to edit the definition of the feature, then "unselect" the offending entities. That's how I will usually take care of things like a surface that is mistakenly included (usually an extra plane I didn't know I'd selected) or a bad hole axis, etc.