We’ve recently made changes to the create_group mutation and deprecated the position argument 
If you still want to specify the location of the new group on the board, you can use the recently released relative_to and position_relative_method arguments. Check out our documentation to read more about each of these new arguments and see them in action!
mutation {
create_group (board_id: 1234567890, group_name: "new group", relative_to: "test group", position_relative_method: before_at) {
id
}
}