Fix the issue with ViewportTexture assignment

For properties like `ViewportTexture.viewport_path` that enable
`PROPERTY_USAGE_NODE_PATH_FROM_SCENE_ROOT`. The case of enabling
**Editable Children** to edit nodes in a child scene seems to have
been overlooked before.

The `EditorPropertyResource` also missed the **Editable Children**
case when handling `ViewportTexture`.

(cherry picked from commit c3a61d531fe041e939ecc109cea7a20e44876567)

editor/inspector/editor_properties.cpp

@@ -3242,15 +3242,29 @@ Node *EditorPropertyNodePath::get_base_node() {
 			}
 		}
 	}
-	if (use_path_from_scene_root) {
-		if (get_edited_object()->has_method("get_root_path")) {
-			base_node = Object::cast_to<Node>(get_edited_object()->call("get_root_path"));
-		} else {
-			base_node = get_tree()->get_edited_scene_root();
-		}
+
+	if (!use_path_from_scene_root) {
+		return base_node;
 	}
 
-	return base_node;
+	if (get_edited_object()->has_method("get_root_path")) {
+		return Object::cast_to<Node>(get_edited_object()->call("get_root_path"));
+	}
+
+	if (!base_node) {
+		return nullptr; // Editing external resources.
+	}
+
+	if (base_node->is_instance()) {
+		return base_node; // Known scene root.
+	}
+
+	base_node = base_node->get_owner();
+	if (base_node) {
+		return base_node; // Node in known scene.
+	}
+
+	return get_tree()->get_edited_scene_root(); // Treat as a node in the main scene.
 }
 
 EditorPropertyNodePath::EditorPropertyNodePath() {
@@ -3354,6 +3368,17 @@ void EditorPropertyResource::_resource_changed(const Ref<Resource> &p_resource)
 		}
 	}
 
+	if (p_resource.is_valid() && p_resource->is_local_to_scene()) {
+		// Attempting to configure the local scene.
+		Node *local_scene = _get_base_node();
+		if (local_scene) {
+			HashMap<Ref<Resource>, Ref<Resource>> remap;
+			p_resource->configure_for_local_scene(local_scene, remap);
+		} else {
+			WARN_PRINT("You are attempting to assign a local-to-scene resource outside the scene.");
+		}
+	}
+
 	// The bool is_script applies only to an object's main script.
 	// Changing the value of Script-type exported variables of the main script should not trigger saving/reloading properties.
 	bool is_script = false;
@@ -3471,6 +3496,39 @@ bool EditorPropertyResource::_should_stop_editing() const {
 	return !resource_picker->is_toggle_pressed();
 }
 
+Node *EditorPropertyResource::_get_base_node() {
+	Node *base_node = Object::cast_to<Node>(get_edited_object());
+
+	if (!base_node) {
+		base_node = Object::cast_to<Node>(InspectorDock::get_inspector_singleton()->get_edited_object());
+	}
+
+	if (!base_node) {
+		// Try a base node within history.
+		if (EditorNode::get_singleton()->get_editor_selection_history()->get_path_size() > 0) {
+			Object *base = ObjectDB::get_instance(EditorNode::get_singleton()->get_editor_selection_history()->get_path_object(0));
+			if (base) {
+				base_node = Object::cast_to<Node>(base);
+			}
+		}
+	}
+
+	if (!base_node) {
+		return nullptr; // Editing external resources.
+	}
+
+	if (!base_node->get_scene_file_path().is_empty()) {
+		return base_node; // Known scene root.
+	}
+
+	base_node = base_node->get_owner();
+	if (base_node) {
+		return base_node; // Node in known scene.
+	}
+
+	return get_tree()->get_edited_scene_root(); // Treat as a node in the main scene.
+}
+
 void EditorPropertyResource::_viewport_selected(const NodePath &p_path) {
 	Node *to_node = get_node(p_path);
 	if (!Object::cast_to<Viewport>(to_node)) {
@@ -3481,7 +3539,9 @@ void EditorPropertyResource::_viewport_selected(const NodePath &p_path) {
 	Ref<ViewportTexture> vt = get_edited_property_value();
 	ERR_FAIL_COND(vt.is_null());
 
-	vt->set_viewport_path_in_scene(get_tree()->get_edited_scene_root()->get_path_to(to_node));
+	Node *local_scene = _get_base_node();
+	ERR_FAIL_NULL(local_scene);
+	vt->set_viewport_path_in_scene(local_scene->get_path_to(to_node));
 
 	emit_changed(get_edited_property(), vt);
 	update_property();

editor/inspector/editor_properties.h

@@ -746,6 +746,7 @@ class EditorPropertyResource : public EditorProperty {
 	void _resource_selected(const Ref<Resource> &p_resource, bool p_inspect);
 	void _resource_changed(const Ref<Resource> &p_resource);
 
+	Node *_get_base_node();
 	void _viewport_selected(const NodePath &p_path);
 
 	void _sub_inspector_property_keyed(const String &p_property, const Variant &p_value, bool p_advance);