I'm trying to include a file like this:
{!../../shared-snippets/xref-snippet.md!}

The file appears correctly in the home page, so I know it should work. I can't find any examples of include file with paths to other folders.

Here's the warning I get:

Warning: could not find file ..\shared-snippets\xref-snippet.md. Ignoring include statement. Error: [Errno 2] No such file or directory: '..\\shared-snippets\\xref-snippet.md'