Ah, thanks – I was doing the search wrong. I have attached a screenshot for those not familiar with LinkedIn. If you put “Writing Group” in the Search field and hit enter, it will default to searching companies. If you type in “Writing” and then let LinkedIn do its thing, it will give you a dropdown box and you can choose “Writing in Groups”.
I have been out of the corporate world for a couple of years, so I was rusty, and I imagine some writers may not have used LinkedIn for other roles. Hope this helps.