Did you maybe forget to push everything? I can't see where the id should be added to the overview. You've simply added a new data attribute that is not used anywhere.
Actually that's everything. Just wanted to add the website ID to hide it with an userscript from the overview. Maybe we could add a setting to hide in the Piwik settings -> Website -> Manage?
@DevDaveo Could you also display this ID in the tooltip on the Sparkline at the end of each row? Currently reads "Go to dashboard of SITE_NAME" ---> "Go to dashboard of SITE_NAME (Website id XYZ)"
please check my previous comment. For now i'll close the PR but we are happy to merge if you can apply the feedback. Thanks!