Attaching Metadata, Tags, and Ratings in the Organizer - My Photoshop Elements 13 - page 130

Create Subcategories
If you choose the New Sub-Category command from the keyword cat-
egory pop-out menu, you can create a subcategory under a Keyword Cat-
egory to further group and organize your photos and videos.
10. In the Create Category window, click Choose Color to choose a color using the
Color Picker.
11. Click in the Category Name field and type a new category name.
12. Click and drag the slider left or right to see all default icons.
13. Click to choose the one you want for your keyword category.
14. Click OK to close the window. The new keyword category displays in the Tags
pane.