You can upload a formerly downloaded or even a manually created file directly through the web frontend. Given sufficient permissions, the Dashboard provides a related link:
This can be any file:
It should be valid of course, but don't worry - Icinga Business Process Modeling protects you from syntax errors:
Just for fun you could try to upload an image or whatever you want - it will not break. It will also protect you from accidentally overwriting existing files:
So in case you need to replace an existing process, please delete it before uploading a new one.