@gfranco currently it is not possible to add Categories to NWC forms in Nintex Mobile the same way that you can with O365, however we do have a feature request for this functionality that is now open for voting if you would like to add your vote to the count:

https://nintex.uservoice.com/forums/430063-5-nintex-workflow-cloud/suggestions/35968468-add-category-for-nintex-mobile

Thank you @butlerj, I will vote on uservoice.

Wondering if there is any update to this 4 years later?

I can see the User voice link is now broken.

Hi @Bards,

We have moved the suggestions submission from UserVoice to Nintex Ideas.
The suggestion mentioned above is now here: https://ideas.nintex.com/ideas/IDEA-I-3061