Good Morning,

I would like to know how can I add a third matrix scale in a table?

There is no way to do that with core functionality. I suppose you cold use JavaScript and CSS to make 3 separate arrays appear as one but it would require significant coding to handle validation, etc. and it would be virtually unusable on mobile devices.

Hi,
you can use an array(number) with dropdowns.



Same functionality, a bit different in look and feel.

Regards
Joffm

But this will only work if all scales are the same, right?

Yes, but IMO some usual dual scale arrays are like:
1. Importance (1=very important, 5 = not impostant at all)
2. Satisfaction (1=very satisfied, 5 = not satisfied at all)

Therefore I thought the third will be something similar.

Joffm

I agree, I just wanted to highlight the caveat of this aproach.