AutoCAD Electrical toolset provides five predefined PLC styles, numbered 1 through 5. You can create an additional style or modify an existing style. About three dozen symbols are associated with each predefined style. In the library folder, these symbols are located in files named HP#*.dwg, where "#"is the style number.
An easy way to create a PLC style is to copy the library symbols of an existing PLC style to one of the unused style numbers (6, 7, 8, or 9) and then edit each one to suit your needs.
For example, copy style 1 to style 6 by copying \Users\Public\Documents\Autodesk\Acade {version}\libs\{library}\hp1*.dwg to \Users\Public\Documents\Autodesk\Acade {version}\libs\{library}\hp6*.dwg.
Open the hp6*.dwg drawing files in AutoCAD and modify as required. To access your new style, select "6" in the style sub dialog box when you prepare to select and insert a new PLC module.
The icon menu graphics that display for the various PLC styles are bitmap files saved to your \Program Files [(x86)]\Autodesk\AutoCAD {version}\Acade\ folder where AutoCAD Electrical toolset's Insert PLC and Drawing Properties tools can access them.