The Whos Online block has a Filter By function which displays all user groups, primary and secondary.

It would be nice if there was a way to filter who can filter, and what filters they are able to see. 

Thank you for your consideration.

Could I ask what the reason is you would want this? I ask as you can make unsearchable groups at a group level, and wondered if that was the reason

58 minutes ago, Marc Stridgen said:

Could I ask what the reason is you would want this? I ask as you can make unsearchable groups at a group level, and wondered if that was the reason

I cant prevent secondary groups from showing in the filter?

In any filter. Go to the group in the admin CPand switch off "Allow filtering by group" on the first tab

1 hour ago, Marc Stridgen said:

In any filter. Go to the group in the admin CPand switch off "Allow filtering by group" on the first tab

Fantastic, thank you.

No problem at all 🙂