Think I may have sorted this. By duplicating and then modifying further SendGrid blocks they all use the same API key. Then you can create different emails which apply to different grids, referenced by each different block.
I’ve had the same issue. Pretty bad it seems to me if you can only send one email template per API key. I’d expect to have a library of templates then pick the relevant one for a particular grid view, but all using the same block.
