How to use the Metabox user dashboard for moderation

Hi,

First, try to modify WP_Query arguments with rwmb_frontend_dashboard_query_args (check docs); e.g., adding this would let the moderator see all posts:

$args['author'] = 0;

You will have to use conditions within above-mentioned filter to allow only selected users/roles see all posts in a dashboard.

Next, not sure what you mean by "moderation", is it to hide/publish the post? If so, I use custom field group with radio buttons having options corresponding with post status, e.g., "publish", "draft". The field group is then assigned to a post type. Upon submitting the form, you might fire wp_update_post to update post status according to the option selected in the form's field group with rwmb_after_save_post action (see docs).