Loving pi-hole, but query log could be better. A lot of applications have the option to filter on info, error and warning. I'd love to see something like that in pi-hole and especially per client. It's easier to see why a site is not working when you can filter out everything but blocked for device.
Info - OK forwarded
Warning - OK insecure
Error - blocked
Does this not already exist in the query log? First, click on the client to filter by that client. Then sort by status (either ascending or descending).