It seems the pages Live Editing Zen Theme and Submission Guidelines from the docs are outdated.

In Submission Guidelines:

• The link to the submission page is broken.

In Live Editing Zen:

• Using Twilight, I couldn't find userChrome.css in the debug StyleEditor, even though the file exists in chrome/ folder. Modifying userChrome.css directly has no effect on Zen even after a restart.
• I was able however to test my mod by clicking the "+" button to "Create and append a new style to this document" which gives me a temporary file, this works but the mod isn't saved after a restart.

Can we get some information about what is going on with Mods?