To edit a pinned message you need to open the Pinboard tab and right-click on the pin you wish to edit (or click on the tiny blue arrow in the top-right corner of the pin). From the drop-down menu that appears, choose "Edit".
Once you’re finished with the editing bit, hit "Save" and you’re good to go!
To remove a pinned message from the Pinboard you need to delete it. To do this, open the Pinboard tab and right-click on the pin you wish to delete. From the drop-down menu that appears choose "Delete".
Once you’ve confirmed the deletion in the popup that appears, the pinned message will disappear from the Pinboard.
Alternatively, if you don't want to delete the pin, but simply move it out of sight, then you can rearrange it by dragging and dropping it to a different location on the Pinboard.
Note that all members of the conversation can Edit, Delete and rearrange the pinned messages on the Pinboard.
Read more on our blog: Pinboards - to pin or not to pin?