I realize that many plugins can get overdone, trying to do too much. But, this plugin suffers the opposite.
I recommend expanding this plugin so that the site ID shows everywhere it might be useful. The most intuitive places I can think of to show the site ID are the list of sites (/wp-admin/network/sites.php) and, though slightly redundant, on the site information page (/wp-admin/network/site-info.php).
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