If you are having the access rights of workitem configuration, then you will able to add/remove workitem category.
To add a workitem category,
1. Click on Add Category.
2. Give an appropriate name.
3. Select a system-generated icon.
4. Click on Save.
Users can delete any workitem category. To delete any category type click on Delete icon.
Category Type Name:
Name the workitem category, that you have added for instance: Meeting.