Hello Kait363636,
Thank you for reaching out to the Microsoft community!
Based on the information you have shared with is I understand that you have a concern regarding sharing categories for a shared to do list.
As this issue is more related to the Microsoft to Do. I would recommend post this query in our dedicated community for Microsoft To Do. You will be able to find specialized experts in this matter that can provide unique solution to this issue.
You can use the following link to post the query in Microsoft To Do | Microsoft Community Hub
I apologize for redirecting you to a different community. I believe this step will ensure faster and more accurate assistance for your specific scenario.
I appreciate your patience and understanding. Have a great day!