Create sub-app which lists messages requiring moderation.
(Like we had it on magnolia 4.5 / forum 1.3.x; see attachment; note that the last version on magnolia 4.5.x might be buggy in showing these).

Mainly, the list should show the messasges which have not been validated yet, if validation aka activation is required (which can be configured; per default it IS required).
Messages which have been deactivated (after they were active once) should appear on the list, too.

so, the sub-app will be very similar to the 1st sub-app, but only show messages that require validation aka activation.
Actions and actions-availability will be configured in its superclass.

This means; this subapp(-config) should extend the one from the 1st/main subapp (called "browser")
But custumize content-presenter-defs. and presenter classes to filter the content (by adding implementationClass-property for the content-views, ...)