The shortcut for the sidebar is Ctrl+Shift+/ which prevents it from being able to be utilized at all on Nordic keyboards (and likely others), since slash requires you to press Shift+7.
Unfortunately, as far as I know, there's no way to rebind hotkeys in Edge. I tried rebinding the shortcut using AutoHotkey, but not even that seems to work. Although let's be honest, you shouldn't need a workaround for basic shortcuts in a browser.
Please add an alternative shortcut. Ctrl+Shift+. works, period is right next to comma which is used for the vertical tabs shortcut so it would make a lot of sense.