I really liked Github left side explorer - I can speed up to work in building queries and explanatory the graph options.
how can I enable it on Graphiql or Github implement/extending this graphiql feature

It's a GraphiQL's plugin, you can install and use it as a plugin with your own GraphiQL interface.
@Nishchit14 is there a guide on how to install this?
yes! just follow this example:
Most helpful comment
It's a GraphiQL's plugin, you can install and use it as a plugin with your own GraphiQL interface.