The each I/O register can be categorized (by folders) and displayed in the tree view.

Move the caret to the I/O register name to create a new category then click the button in the toolbar and directly enter the new category name.

Click the category name to edit, and click it again, then directly modify the category name from the keyboard.

Select categories to delete then click the button in the toolbar.

However, the categories that can be deleted are only the empty categories.

I/O register name is categorized when I/O register is dragged and dropped in the category.

Also, the display order of the categories and the I/O register names (upper or lower position) can be changed easily by drag and drop operation.