Add category field to Edit/Submit Campaign?

Hi!

I would like to add a Categoy field to the Edit/Submit Campaign.
So far I have made ??the following changes in shortcode-submit.php file :
– I added this line in the register_fields() function:

'category' => array(
				'label'       => __( 'Category', 'atcf' ),
				'default'     => null,
				'type'        => 'select_cat',
				'editable'    => false,
				'placeholder' => null,
				'required'    => true,
				'priority'    => 6
			),

– I added this line in the function __construct() :
add_action( 'atcf_shortcode_submit_field_select_cat', 'atcf_shortcode_submit_field_select_cat', 10, 4 );
– I created the function to generate the html code:

[...]
?>
	<p class="atcf-submit-campaign-<?php echo esc_attr( $key ); ?>">
		<label for="<?php echo esc_attr( $key ); ?>"><?php echo apply_filters( 'atcf_shortcode_submit_field_label_' . $key, esc_attr( $field[ 'label' ] ) ); ?></label>

		<select name="<?php echo esc_attr( $key ); ?>">

		<?php
				$terms = get_terms( 'download_category' );
				if ( count( $terms ) > 0 ) {
						/*echo "<option value=''>" . __( 'Show all categories', 'edd' ) . "</option>";*/
						foreach ( $terms as $term ) {
							$selected = isset( $_GET['download_category'] ) && $_GET['download_category'] == $term->slug ? ' selected="selected"' : '';
							echo '<option value="' . esc_attr( $term->slug ) . '"' . $selected . '>' . esc_html( $term->name ) .' (' . $term->count .')</option>';
						}
				}
		?>
		</select>
	</p>
<?php
}
[...]

The problem is, like you will know, that actually the selected category is stored in the BBDD as a extra field (campaign_category) but not as the real category.
Can you help me please?
Thank you!

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