DOC Updated Nested GridField docs

docs/en/index.md

@@ -159,14 +159,148 @@ Nested GridFields
 The `GridFieldNestedForm` component allows you to nest GridFields in the UI. It can be used with `DataObject` subclasses
 with the `Hierarchy` extension, or by specifying the relation used for nesting.
 
+Here is a small example of basic use of Nested GridField.
+
+```php
+class MyAdmin extends ModelAdmin
+{
+    ...
+
+    public function getEditForm($id = null, $fields = null)
+    {
+        $form = parent::getEditForm($id, $fields);
+
+        $grid = $form->Fields()->dataFieldByName(MyObject::class);
+        // Add Nested GridField to main GridField
+        $grid->getConfig()->addComponent(GridFieldNestedForm::create());
+
+        return $form;
+    }
+}
+```
+
+There are several ways to use Nested GridField. The implementation depends on the type of data you will be using in your GridField.
+For instance, if there is a DataObject that has the [`Hierarchy`](api:SilverStripe\ORM\Hierarchy\Hierarchy) extension, you can use the following approach.
+
+As an example, here we can use a typical hierarchy of Security Groups, where another Group can serve as a parent.
+
+```php
+class MySecurityAdminExtension extends Extension
+{
+    public function updateGridFieldConfig($config)
+    {
+        if ($this->owner->getModelClass() === Group::class) {
+            $config->addComponent(GridFieldNestedForm::create()->setRelationName('Members'));
+        }
+    }
+}
+```
+
+```yml
+SilverStripe\Admin\SecurityAdmin:
+  extensions:
+    - MyApp\MyExtensions\MySecurityAdminExtension
+```
+
+Another way to use Nested GridField together with DataObjects that do not have the `Hierarchy` extension but have `has_many` relationships with other objects.
+Let's say you have the following DataObject that has multiple levels of relationships, and an Admin section where the data of this object will be displayed.
+You want the user to be able to view information regarding this object and all nested objects on the same page, without the need to navigate to each object individually.
+In this case, you can use the following approach.
+
+```php
+class ParentNode extends DataObject
+{
+    ...
+
+    private static $has_many = [
+        'ChildNodes' => BranchNode::class,
+    ];
+}
+
+```
+
+```php
+class ChildNode extends DataObject
+{
+    ...
+
+    private static $has_one = [
+        'ParentNode' => ParentNode::class,
+    ];
+
+    private static $has_many = [
+        'GrandChildNodes' => GrandChildNode::class,
+    ];
+
+    public function getNestedConfig(): GridFieldConfig
+    {
+        $config = new GridFieldConfig_RecordEditor();
+        $config->addComponent(GridFieldNestedForm::create()->setRelationName('GrandChildNodes'));
+        return $config;
+    }
+}
+
+```
+
+```php
+class GrandChildNode extends DataObject
+{
+    ...
+
+    private static $has_one = [
+        'ChildNode' => ChildNode::class,
+    ];
+}
+
+```
+
 ```php
-// Basic usage, defaults to the Children-method for Hierarchy objects.
-$grid->getConfig()->addComponent(GridFieldNestedForm::create());
+class MyAdminSection extends ModelAdmin
+{
+    private static string $url_segment = 'my-admin-section';
+    private static string $menu_title = 'My Admin Section';
+
+    private static array $managed_models = [
+		RootNode::class
+	];
+
+    protected function getGridFieldConfig(): GridFieldConfig
+    {
+        $config = parent::getGridFieldConfig();
+        $config->addComponent(GridFieldNestedForm::create()->setRelationName('ChildNodes'));
+
+        return $config;
+    }
+}
 
-// Usage with custom relation
-$grid->getConfig()->addComponent(GridFieldNestedForm::create()->setRelationName('MyRelation'));
 ```
 
+There is also the possibility to use Nested GridField with the data structure ArrayList. To do this, you can use the following approach.
+
+```php
+class NonRelationalData extends DataObject
+{
+    private static $table_name = 'NestedGridField_NonRelationalData';
+
+    private static $db = [
+        'Name' => 'Varchar(50)',
+    ];
+
+    public function getList() {
+        $list = ArrayList::create();
+        $data = Company::get()->byIDs([1,2,3,4,5]);
+        foreach ($data as $value) {
+            $list->push($value);
+        }
+
+        return $list;
+    }
+}
+
+```
+
+#### Additional features and settings
+
 You can define your own custom GridField config for the nested GridField configuration by implementing a `getNestedConfig`
 on your nested model (should return a `GridField_Config` object).
 ```php
@@ -185,7 +319,8 @@ class NestedObject extends DataObject
 ```
 
 You can also modify the default config (a `GridFieldConfig_RecordEditor`) via an extension to the nested model class, by implementing
-`updateNestedConfig`, which will get the config object as the first parameter.
+`updateNestedConfig`, which will get the config object as the parameter.
+
 ```php
 class NestedObjectExtension extends DataExtension
 {
@@ -195,3 +330,10 @@ class NestedObjectExtension extends DataExtension
 	}
 }
 ```
+
+You can set the maximum number of nested levels using a `$default_max_nesting_level` configuration property. The default value is 10 levels.
+
+```yml
+Symbiote\GridFieldExtensions\GridFieldNestedForm;
+    default_max_nesting_level: 5
+```