Currently only arrays are supported.
When sent a request with arrays as variables I get the following error: body: { error: { message: 'Argument 1 passed to GraphQL\\Validator\\Rules\\QueryComplexity::setRawVariableValues() must be of the type array, string given, called in /portal/library/composer/webonyx/graphql-php/src/GraphQL.php on line 62 and defined' } } }.
Any reason why only arrays are allowed if this is intentional? If not it should support both formats.