UML question for inXML-XSL-outXML

Question

IDE

I want to see the connection between the elements of the incoming and outgoing document through the prism of xsl.
I try in Stylus now I will try in Altova.
If there are more visual and GNU ways, then please advise.
It's just that the stylesheet is large and often changed by the customer, I would like to print the links on the poster (for clarity) and change the play as it goes.