Hello  @mohanned_neamah ​ - 

I don't have any of the editing powers in the Community that others have, but I am replying to this in hopes that it moves up a list and perhaps prompts others to say something, given that you have not received a response yet.  It appears that you have stumped the Community so far, and perhaps someone who knows the right people to "tag" at Instructure can bring this to their attention.  But you are absolutely correct; there is no way to do this from all appearances, and yet it is a setting that exists when creating a graded Assignment or graded Discussion.  My guess is it may be because Canvas does not "know" how much the quiz will be worth until all of the questions and their respective point values have been input into the QUESTIONS area of a quiz, but still--one would think that you can edit it later and then have that as an option.  I was reminded of seeing your question because of a somewhat similar question posed here:  Is it possible to view quiz results as a percentage instead of points correct?

I'm beginning to wonder if the best option may be to create a Feature Idea as outlined here: How do I create a new feature idea?