How to change the CSV delimiter

GravityImport will automatically try to detect the four commonly used delimiters: \t (tab), | , ; , and , (serves as the default delimiter when none can be detected).

You can also specify a custom delimiter (e.g., @ ) by using the gravityview/import/config  filter:

add_action( 'gravityview/import/config', 'change_gravityimport_delimiter' );

function change_gravityimport_delimiter( $config ) {
	$config->setDelimiter( '@' );
}

Not sure where to add that code? Here's where to add code samples.