If you like to add a command to the menu or to a toolbar or if you like to assign a shortcut to a function, you first have to select a command category (function category) and then to select the command (function) itself. 

Suppose you only know the name of a command (e.g. from the menu or from an icon tip) and you like to use this command for customization purposes. In a lot of cases the corresponding category is obvious. But there also examples where it is not obvious. An example is the command “Apply Style”. First I would expect to find this command in the category Format but it is in Documents. In order to find such commands you have to browse laboriously different categories. For these cases an alphabetical list of all commands would be helpful. 

An easy solution for such a list could be a help page, where at each command the corresponding category is noted. It should be possible to open this list directly by a button in the “Add Commands” dialogue, respectively “Customize → Keyboard” dialogue.

Another possibility is a function which enables the user to switch between 2 modes in the “Add Commands” dialogue, respectively “Customize → Keyboard” dialogue. One mode would be the existing mode (categories and commands are displayed), in the other mode all commands would be listed in alphabetical order without displaying the categories.