app/Models/Traits/SelectHierarchyTrait.php
public static function getRenderedNode(Node $node)
    {
        $options = [];

        if ($node->isRoot()) {
            $name = $node->name;
        } else {
            $depth = str_repeat('--', $node->depth);

            $name = sprintf('%s %s', $depth, $node->name);
        }

        $options[$node->id] = $name;

        if ($node->children()->count() > 0) {
            foreach ($node->children as $child) {
                $options = $options + static::getRenderedNode($child);
            }
        }

        return $options;
    }
public static function getRenderedNode(Node $node)
    {
        $options = [];

        if ($node->isRoot()) {
            $name = $node->name;
        } else {
            $depth = str_repeat('--', $node->depth);

            $name = sprintf('%s %s', $depth, $node->name);
        }

        $options[$node->id] = $name;

        if ($node->children()->count() > 0) {
            foreach ($node->children as $child) {
                $options = $options + static::getRenderedNode($child);
            }
        }

        return $options;
    }
Renders the specified category and it's children in single dimension array.

@param Node $node

@return array