Configure GraphQL
Configure API With GraphQL Protocol, and Publish it.

Query Method Execution
For Executing Method of Odoo using GraphQL, we have to provide "Method" in mutation of GraphQL, where we have to provide model as per GraphQL Query with method_name and method_parameters.
GraphQL Query:
mutation Method {
methodSaleOrder: SaleOrder(
id: 21,
method_name: "action_draft",
method_parameters: {}
){
id
}
}