Filter that changes the parsed attribute values of navigation blocks contain typographic presets to contain the values directly.

function block_core_navigation_typographic_presets_backcompatibility( $parsed_block ) {
	if ( 'core/navigation' === $parsed_block['blockName'] ) {
		$attribute_to_prefix_map = array(
			'fontStyle'      => 'var:preset|font-style|',
			'fontWeight'     => 'var:preset|font-weight|',
			'textDecoration' => 'var:preset|text-decoration|',
			'textTransform'  => 'var:preset|text-transform|',
		);
		foreach ( $attribute_to_prefix_map as $style_attribute => $prefix ) {
			if ( ! empty( $parsed_block['attrs']['style']['typography'][ $style_attribute ] ) ) {
				$prefix_len      = strlen( $prefix );
				$attribute_value = &$parsed_block['attrs']['style']['typography'][ $style_attribute ];
				if ( 0 === strncmp( $attribute_value, $prefix, $prefix_len ) ) {
					$attribute_value = substr( $attribute_value, $prefix_len );
				}
				if ( 'textDecoration' === $style_attribute && 'strikethrough' === $attribute_value ) {
					$attribute_value = 'line-through';
				}
			}
		}
	}

	return $parsed_block;
}