Error: Permalink Already in Use!

Hi @suffianshakoor

Unfortunately, there is no out-of-box solution available. You can however try to use the below code snippet and control how the new custom permalinks are generated.

After you implement it, whenever a new custom permalink is generated for a new item, the default permalink for it will be forced to be unique:

function pm_unique_permalinks( $default_uri, $native_slug, $element, $post_name, $native_uri ) {
	global $permalink_manager_uris;

	// Ignore native permalinks
	if ( $native_uri ) {
		return $default_uri;
	}

	// Store all the custom permalinks in a separate variable
	$uris = $permalink_manager_uris;

	// Exclude this element
	if ( ! empty( $element->ID ) && ! empty( $uris[ $element->ID ] ) ) {
		unset( $uris[ $element->ID ] );
	} else if ( ! empty( $element->term_id ) && ! empty( $uris[ $element->term_id ] ) ) {
		unset( $uris["tax-{$element->term_id}"] );
	}

	do {
		$duplicates_ids       = array_keys( $uris, $default_uri );
		$duplicates_ids_count = count( $duplicates_ids );

		if ( ! empty( $duplicates_ids_count ) ) {
			preg_match( '/(.+?)(?:-([\d]+))?(\.[^\.]+$|$)/', $default_uri, $parts );
			$index = ( ! empty( $parts[2] ) ) ? $parts[2] + 1 : 2;

			$default_uri = preg_replace( '/(.+?)(?:-([\d]+))?(\.[^\.]+$|$)/', '$1-' . $index . '$3', $default_uri );
		}
	} while ( $duplicates_ids_count > 0 );

	return $default_uri;
}
add_filter('permalink_manager_filter_default_post_uri', 'pm_unique_permalinks', 999, 5);