you don't have to add a point.
You should move the mouse over the first line and then the second one. Then move the mouse approximately to the intersection. When the cursor change, click LMB. See the attached video.
In my opinion sometime very difficult to find the intersection, because I have to estimate "by my eye" where is the intersection point. I would also like to know about a better solution.
I hope somebody know about a switch somewhere, which show all of the intersection points on a view
It depends on what you are trying to do. If you are adding a line or sketch element, you can hove over the two lines and then find the intersection. If you are trying to dimension to the Theoretical Sharp Corner, you may need to insert a point. See video below.
EDIT: My response is for the part environment but it looks like you were seeking an answer in Draft which has been addressed in previous posts.