D Cartwright

Included component allows group admins to easily promote/demote/ban members from all their groups.
It can be further extended using the standard buddypress profile subnav registration functions (for example, the bp-wiki plugin hooks into this to enable movement of wiki pages between groups).

BuddyPress Frontend Admin

This plugin brings site-wide-like administration options to the frontend, allowing group admins simpler management of all of their groups.

itthinx

This plugin redirects 404’s caused by hits on pages that are protected by <a href="https://wordpress.org/plugins/groups/" rel="ugc">Groups</a>.
The redirection settings can be adjusted in Settings > Groups 404 :
Visits to protected pages can be redirected to:
<ul>
<li>a specific post, or</li>
<li>the WordPress login</li>
</ul>
The redirection can also be applied for restricted categories, tags and other taxonomy terms if <a href="https://www.itthinx.com/shop/groups-restrict-categories/" rel="nofollow ugc">Groups Restrict Categories</a> is used.
The redirect status code can be selected among:
<ul>
<li>Moved Permanently (301)</li>
<li>Found (302)</li>
<li>See other (303)</li>
<li>Temporary Redirect (307)</li>
</ul>

Groups 404 Redirect

I know this plugin hasn't been updated in a couple years, but IMHO Groups and its related plugins (like this one) are a hidden gem for WordPress sites. So many people jump to complicated membership plugins when they could do everything they need with Groups. This 404 redirect add-on works like a charm. I'm using it on the latest version of WP 5.x

Perfect.

Redirect 404's when a visitor tries to access a page protected by Groups.

BuddyPress Frontend Admin vs Groups 404 Redirect