I often use the "Rename Symbol under Cursor" for classes and functions.
I also like your extension of the renaming process to comments/documentation (doxygen style), too.

How about extending this refactoring option to parameters of functions, too?

I think we already have it partly implemented:

If you edit the parameter name of a variable in the declaration a hint (bulb) comes up with the option (Alt+Enter) to adapt the signature of the definition.

When you choose this, the name of the parameter is changed in the definition of the function and in the body of the function. Great

But how about using a "Rename Symbol under Cursor" for function parameters, too?
So you could see, what will be changed in the declaration and in the definition and in the documentation of the function (e.g. the @param parameter_name)?

You could even use it in the function body: Select a variable in the body that is a parameter of a function and use "Rename Symbol under Cursor"?