COPYTAG is the optional TAG copy attribute. When AutoCAD Electrical updates a TAG1, TAG2 or TAGSTRIP attribute, it also looks for and updates any COPYTAG attributes present on the symbol with a copy of the TAG text. A special replaceable parameter, "%T", can be encoded onto the COPYTAG attribute prompt value of the definition. It allows for adding a suffix and/or prefix to the TAG text. If you need more than one extra TAG copy on a symbol, name the attributes COPYTAG01, COPYTAG02, and so on. If there is no prompt value encoded on the attribute definition, AutoCAD Electrical simply applies a copy of the tag-ID to the COPYTAG* attributes.
For example, you create a large "drive" schematic symbol with a TAG1 attribute for the tag-ID of the drive. You want some other parts of this single symbol to carry the TAG1 value plus a suffix like "-POT" and "-DBRES". On your library symbol, insert an attribute definition "COPYTAG01" with a prompt value of "%T-POT" near the potentiometer graphic of the symbol and "COPYTAG02" with a prompt value of "%T-DBRES" near the dynamic braking resistor graphic. When this symbol is inserted on a schematic drawing, and a TAG is assigned, AutoCAD Electrical automatically updates each COPYTAG* attribute accordingly.