Add custom metadata to Easy Digital Downloads (EDD) file downloads

edd_file_download_meta.php

<?php

function drw_edd_create_file_row($post_id, $key, $args) { ?>
	
	<div class="edd-form-group edd-your_meta_key">
		<label for="edd_download_files-<?php echo esc_attr( $key ); ?>-your_meta_key" class="edd-form-group__label edd-repeatable-row-setting-label"><?php esc_html_e( 'Your Meta Title', 'easy-digital-downloads' ); ?></label>
		<div class="edd-form-group__control">
			
		<?php
		
		$select_args = array(
		    'options' => array(
			    'option_1' => 'Your Option',
			    'option_2' => 'Your Second Option'
		    ),
		    'name'             => 'edd_download_files[' . $key . '][your_meta_key]',
		    'class'            => 'edd-form-group__input edd_repeatable_your_meta_key_field',
		    'id'               => 'edd_download_files-' . $key . '-your_meta_key',
		    'selected'         => isset($args['your_meta_key']) ? $args['your_meta_key'] : null,
		    'value'            => isset($args['your_meta_key']) ? $args['your_meta_key'] : null,
		    'placeholder'      => __( 'Your Custom Meta Title', 'easy-digital-downloads' ),
		    'show_option_all'  => false,
		    'show_option_none' => false,
		);
		
		// can use EDD()->html->text or any method from the EDD_HTML_Elements class
		// https://easydigitaldownloads.com/docs/edd_html_elements/
		
		echo EDD()->html->select( $select_args );
				
		?>
		
		</div>
	</div>
		
	<?php
	
}

add_action('edd_download_file_table_row', 'drw_edd_create_file_row', 10, 3);

function drw_edd_file_row_args($variables, $value) {
	
	$your_meta_key = isset( $value['your_meta_key'] ) ? $value['your_meta_key'] : '';
	
	$variables['your_meta_key'] = $your_meta_key;
	
	return $variables;
}

add_filter('edd_file_row_args', 'drw_edd_file_row_args', 10, 2);