Is there a way to get the names and values of all parameters passed to
an XSLT transformation? I would like to be able to dump all of them to
a file during the transformation itself without having to hardcode
their names in the XSL fragment that outputs the file.

I am using Saxon-HE 9.2.1.2J and XSLT 2.0. I refer specifically to
custom parameters passed to the stylesheet from the command-line like
"FOO=bar" in:

java -jar saxon9he.jar -xsl:transform.xsl -it:main 'FOO=bar'