How do I add a new Category in pop-up Menu in Numbers?

Yup, they're identical, I just double-checked. I'm not doing something. Can you describe how you would add and use a custom category, step-by-step? I did look this up online but couldn't find the issue.

Thanks so much, Ian

Also, I just entered a new row in the Transactions table, and tried to set to one of my new categories in the third column drop-down, but the new categories I created are missing from the drop-down (and missing from the Pop-Up Menu edit list under the Cell tab in Formatting.) When I click on the row that was selected when I added the categories, they're available from the drop-down there (and showing in the Pop-Up Menu edit list under Format, Cell.) It would make no sense that I'd have to select each cell in the Category column of the transaction sheets one-by-one and manually re-add the new Category name to the Pop-Up menu. This is why I feel I'm missing something.

When I select the entire Category column as you have in the above example screenshot, I do not see the message about selected cells containing different menu items below the Pop-Up Menu drop down under Data Format, as you have. Nor have I merged any previously. This is the first I've seen anything about merging. As I mentioned, I can get new categories to APPEAR on the menu-pop up when I click on the drop-down arrow in a category cell, and even assign the new category to that cell, but it doesn't seem to apply the transaction in that row to the Budget Table.

Do you mean I am, or am not, supposed to select the entire column before adding a new category?