You can now tag several collaborators that are members of the workspace you're in to send them a group message.

To do so, open the Private Messages popup as usual then click on the "+" button.

There, you can use the search bar to look into the member's list and simply click on the members you want to send a private message to. They'll appear as tagged in blue in the search bar.

You can add as many members as you want for a single Group Message ; and create as many groups as needed.

Retrieve your newly created group conversation directly by clicking the back arrow in the top left corner of the private messages popup. You will find the list of all you recent conversations and can use the search bar to find the one you want.

Here is a quick video guide: