When your code contains bracketed words, like [server_name], that are not intended as parameters, you can not edit the code of the program object from the “deploy” tab of a control procedure.
The brackets do not have the function of signifying a parameter here, but to make sure the server name is a qualified name that can include spaces.
Having an option in the control procedure to disable parameter detection would avoid this message and allow you to make changes to the program object (generated) code.
What happens if you use it as a parameter and assign [@servr_name] to it?
it already is, by default