use of GraphQL with REST dataset

Question

I was trying to produce some dashboards upon our gitlab with knowage 8.0.22

I managed to get some REST datasets working using the gitlab REST api, but I was also trying to use graphQL gitlab api, because it's more powerful, than simple REST api...

So far, so good, I tested my request in Postman, I get the data I request, so I try in a REST type dataset in knowage, if I do something wrong, no token, or bad url, I've an answer from gitlab, 

but when I perform the right request (the one that works with postman, whatever I set to grab data through jsonpath, I got nothing, like the gitlab response is empty...

I will check logs on gitlab side, but I think it answer the graphQL request....

1. I wonder how to check from knowage logs what is received, or the size, probably by setting the knowage component to DEBUG logging level, but which component for dataset ?...
2. Also I'd like to know if someone has already tried to use successfully GraphQL with knowage REST dataset...

Thanks in advance for any suggestion !