Sorry, never mind, figured it out.

Where pHL7 is the EnsLib.HL7.Message, execute:

do pHL7.BuildMap(0)

After that, reference pHL7.GetSegmentPath(*) to get the schema path (replacing * with the segment number, e.g. in the screenshot in my original post, PV1 was row 5, so pHL7.GetSegmentPath(5) = "PIDgrp(1).PV1").

For my loop I'm referencing pHL7.SegCount, e.g:

F i=1:1:pHL7.SegCount { w pHL7.GetSegmentPath(i),! }