The 'Mod Queue' option specifies the name of a file which is written to every time a moderation request is added or dismissed. If the option is set to 'mq', the mod queue will be available at '/mq.html'.
The only contents of the mod queue file is a number which indicates how many moderation requests are currently pending. If there are two new posts and one reported post, the mod queue file will contain '3'.
The purpose of the file is to make it easy for staff to check for pending moderation requests without needing to log in or provide cookies to any automatic monitoring software. Any tool which monitors a page for changes can then be used to monitor moderation requests. Because no details about the posts are included, the file does not need to be password protected.
Tofu, the official thread watcher application, supports monitoring mod queue pages. This makes it easy to moderate multiple instances.
https://codeberg.org/tslocum/tofu