You can add as many keywords as you want and the SEO Live Assistant allows you to place in keywords that you store in Briefcase.
And it will mark the main keyword and the others as well and calculate Optimization score for all of them.
So, maybe you have 1 main keyword, 3 secondary keywords, and 5 other keywords which you want to place inside the blog post, to help Google understand what the content is about (eg. adding “magical wands” “Diagon Alley”, etc. to a post about “Hermione Granger”)
That would be a total of 9. You can manage that as you like and we don’t limit you.