Please update GraphiQL Explorer in GraphiQL Online (https://graphiql-online.com, https://github.com/hasura/graphql-engine/blob/master/community/tools/graphiql-online) to the latest version.

More info about new version: https://www.onegraph.com/blog/2019/05/30/GraphiQL_Explorer_2_0_A_Power_User_Release.html