access mail merge data from any location

This is the macro command that sets up and runs a Merge.

MergeRun (FormFileType: FormFile!; FormFile: "F:\examples\merge\date.frm"; DataFileType: DataFile!; DataFile: "F:\examples\merge\date.dat"; OutputFileType: ToCurrentDoc!)

Other macro commands can identify the folder and name of the current file or enable you to specify a folder and filename/s.
Then the macro could modify the command above to change the choice of merge folders and files.

Indeed... one can use the ?path variable to return the path the macro is in. Provided the merge files are in the same path, something like this would work as a standalone macro:

MergeRun(FormFileType: FormFile!; FormFile: ?Path+"date.frm"; DataFileType: DataFile!; DataFile: ?Path+"date.dat"; OutputFileType: ToCurrentDoc!)

NOTE: This will fail if one puts this into an EMBEDMACRO() merge command as WordPerfect writes the content of the macro to a temporary file, compiles it, then runs it.

I ran a quick check to confirm the behaviour using a merge containing:
EMBEDMACRO(Type(MacroInfo(FileName!)) Hardreturn() Type(?Path) HardReturn() Type(?Name))

One gets back the macro name as a temp file in the temp folder for the user, and blank values for the path and name.

This is because the macro file _IS_ a temp file in the temp folder, and the output file is where the macro is being run, which does not yet have a path or name.