This is something of a ‘note for later’. For some reason my entire side menu (the three vertical dots) was missing from Canary. The following solution both gave me access to the extensions, but returned that menu.
To access extensions in Chrome Canary go to the URL bar and type chrome://flags then search for extensions. There’s a switch we have to flip now for the “Extensions Toolbar Menu”; enable this option. Now you can go the list via the triple dot, More Tools > Extensions. In this screen there’s a triple bar “hamburger” menu that includes a link to the Chrome Web Store.