A group of Microsoft Products and technologies used for sharing and managing content, knowledge, and applications.
Hi
Thank you for your question in this community, I am willing to help you solve your problem, according to your description of the problem:
This Category can be changed. If you just want to add some categories, you can enter them directly in the box, and the content you enter will also be saved and added to the list.
If you want to modify this category, you can follow the steps below:
Click settings>Site contents in the upper left corner
After entering, click Events>CALENDAR>List settings
Find Category under Columns, and then you can manually modify the list you want by yourself
Best Regards
Ethan