One of the nice features of Custom command is the ability to checkout a RO file from any source control software within Kawa. When you try and edit a RO file under Kawa and if there is a custom command by name "Checkout" (not case sensitive) defined then Kawa will automatically prompt you to run the checkout command. If there is no checkout custom command found then Kawa will prompt you to make the file RW. Please make sure the name is exactly as shown above with no ampersand anywhere.
This is just a fringe benefit of setting up custom commands.