Does anyone have a way to add a button to the Tools Menu drop down or any menu for that matter. I would use it for a quicker way to the Advanced Customizer
Instead of doing that, you can just make your own bookmark for the site-wide-customization page in your browser. No need to have the link in the actual Smugmug page. That's how I do it and, as long as I'm already logged in, it takes my right to the advanced customizer page.
I actually have bookmarks for a number of Smugmug-related pages all in one "Smugmug" bookmarks folder: