Dear Paganini_Aus
Thanks for your reply
The Categories is only present on classic outlook for exchange protocol or outlook mailboxes.
If your mailbox is a gmail mailbox, there is indeed no such option.
You can feedback this issue by clicking on the help button on classic outlook and then clicking on feedback. Hopefully in subsequent updates of outlook versions, Microsoft will be able to fix this issue.
Sorry for not confirming your email address with you and causing it to take up your time.
In order to help users with the same issue, would you mind marking “yes” to this reply so that the solution can be quickly located for other users, thank you.
I hope the above information can help you.
Looking forward to your reply.
Best wishes
Clark | Microsoft Community Support Specialist