Quote - Once I have edited the Poser file, how do I get Poser to recognise it as such?   I did do a modification of that kind, but I have only the basic Windows editors.

If you save without compression, then most of Poser's files are plain text.
For one that aren't to big, then WordPad is usable.
Just start WordPad, and then use File | Open to select the file (you'll need to switch the filter to "All Documents (.)" to see files with Poser's extensions).
When you save (work on a copy!), you may get an extra ".TXT" extension added (which needs to be removed).