New DGN files created within Bentley Substation are usually based on the seed files in the "Templates" subfolder of the Substation Data folder. However, DGN files created with the Create Macro tool are based on either the ANSI-IEEE_T.DGN or IEC_T.DGN files in the path below, according to the drawing standard (ANSI-IEEE vs. IEC). The seed file used cannot be specified during macro creation.
A typical path is:
C:\Program Files (x86)\Bentley\Substation V8i\Substation\Promise\template