A Graded Results slide only submits scores from question slides that include Form View. These include the standard Graded Question slides and Freeform Question slides.
The Freeform function lets you build custom question slides. You can find more info here: https://community.articulate.com/series/articulate-storyline-360/articles/articulate-storyline-360-user-guide-how-to-convert-existing-slide-to-freeform-interaction
This post describes methods for submitting the value of a variable: Storyline 360: How to Send the Value of a Variable to an LMS/LRS - Articulate Support
I've also seen multiple posts that discuss using JavaScript to submit custom variable info, so you could search the Forum for that info.