You can't seem to do this from the normal edit page, but have to go to the quick edit page. Irritating. OK I've found it now. Check 'Discussion' in screen options.

I'm surprised this isn't part of WP core. There are a few plugins which address the problem, at least one of which admits to being susceptible to being bypassed by a knowledgeable hacker. It ought to be possible to see how strong a user's password is from the dashboard.

I set this flag so a register button now appears above the log-in button at the bottom of the left-hand menu. Let's see what happens

The root is level 0. We never see it.

The pages in the top menu are level 1. This menu is effectively static.

The menu item for this level two page appears at the extreme left of the side menu.