You cannot use SAS code (or any scripting/automation) to rename items in the process flow -- at least not in any supported manner.
Now, just between us...
Others on this community will point out that an EGP file is a ZIP archive under-the-covers (I'm pre-empting them here!), and you could use various methods to "hack" your change by unzipping/rezipping the file. However, I will tell you that SAS cannot recommend/support that approach since it's risky to use non-SAS tools to modify SAS files; this can result in a corrupted project file.
Always ensure you have a good backup version. Creating backups of project files is an excellent practice anyway.
Chris