The discussion addresses the absence of moderation flags in the old-style admin menu when the admin sidebar is not enabled. RGJ notes that the moderation flags configuration is only accessible via the new admin sidebar, not the legacy horizontal admin nav. tobiaseigen clarifies that the horizontal admin nav is no longer supported and users should transition to the sidebar. RGJ initially misunderstood a suggestion about accessing moderation flags through the ‘Review’ link in the forum sidebar, but tobiaseigen confirms that new admin features require the sidebar. The consensus is that the old admin interface is being deprecated, and users should adopt the new sidebar for full access.
When the admin sidebar menu is not used (i.e. you’re an admin and your group is not in admin sidebar enabled groups ) then the moderation flags configuration at /admin/config/flags is nowhere to be found.
Expected: it can be accessed through the old-style admin menu as well
EDIT related discussion Where to find moderation flags controls? - #14 by Heliosurge
This is not a bug. We are not supporting the horizontal admin nav anymore and everyone should be moving to the admin sidebar. If you want you can acess it using the review link in the forum sidebar.
Maybe add a warning to the setting, or remove the setting ?
That sounded helpful but I’m not seeing it there… 
I see the review link on the sidebar here on meta. Maybe it was added back manually, or removed from your forum? Can you try adding it? I believe it will not be shown to users who do not have access.
We will be deprecating the horizontal nav soon.
Maybe I misread your post. I obviously see the “Review” link but I thought you said that the moderation flags configuration was accessible through that link:
Oh, sorry. I did not read your post carefully enough. I thought you were talking about the review queue.
I think we are understanding each other now. If you want access to new pages being added to the admin interface, you need to use the new admin sidebar.