Hi @NehaGulati,
With the standard rubrics in Canvas, unless you're using some kind of modification script, you can't add a criteria in the middle of others. Unfortunately, you also can't rearrange things, so if you need to add something in the middle it would be a lot of retyping.
The good news is that Instructure is currently developing what they call "enhanced rubrics" which have a lot more features, but also some added complexity because of the extra features. You may or may not have access to these in your Canvas course, depending what your school/institution administrators have enabled for you. You can read more about the enhanced rubrics in the Enhanced Rubrics User Group.
I hope this helps, even if it's not the info you hoped to hear right away.
-Chris