For something like that, say you wanted to snap into this object at specific points. You need to add those points to the vectors where you want the snap to occur. Remember a vector is defined by a start and end. So the visual “line” you see is really just there to conceptualize what the given drawing (set of points with start and ends) is actually creating. So until a point exists, there is no where to snap to.
Take this for example. Maybe you want to snap a line into this shape where I put the pointers.
Look at this now in node editing and you can see there is nothing to snap to. And like I said just a bit earlier, in CAD the line is just there for you to visualize:
So now while in node editing, I can hover over that black line and use the “I” key to insert nodes where I want to define another start / stop point:
With this, I can easily use the line segment tool and connect to these now existing points. One way I recommend seeing this illustrated is to simply draw a line segment anywhere (like what I did here):
Then you can select the shapes all together and in node editing you can see how you can snap those points together:
Now like what @Squid may have been referring to, you have now established a way to cut an end off by node editing. See, now while I am still in node editing, hover over any segment or node and press the “D” key to delete: