Keep Perspective menu open on selection

Makes the Perspective menu consistent with the View menu in the 3D
viewport. This allows for quicker inspection of the scene, and makes
missclicks more forgiving.

editor/plugins/node_3d_editor_plugin.cpp

@@ -4514,6 +4514,7 @@ Node3DEditorViewport::Node3DEditorViewport(Node3DEditor *p_spatial_editor, int p
 	vbox->add_child(view_menu);
 
 	display_submenu = memnew(PopupMenu);
+	view_menu->get_popup()->set_hide_on_checkable_item_selection(false);
 	view_menu->get_popup()->add_child(display_submenu);
 
 	view_menu->get_popup()->add_shortcut(ED_GET_SHORTCUT("spatial_editor/top_view"), VIEW_TOP);
@@ -4537,6 +4538,7 @@ Node3DEditorViewport::Node3DEditorViewport(Node3DEditor *p_spatial_editor, int p
 	view_menu->get_popup()->add_radio_check_shortcut(ED_SHORTCUT("spatial_editor/view_display_lighting", TTR("Display Lighting")), VIEW_DISPLAY_LIGHTING);
 	view_menu->get_popup()->add_radio_check_shortcut(ED_SHORTCUT("spatial_editor/view_display_unshaded", TTR("Display Unshaded")), VIEW_DISPLAY_SHADELESS);
 	view_menu->get_popup()->set_item_checked(view_menu->get_popup()->get_item_index(VIEW_DISPLAY_NORMAL), true);
+	display_submenu->set_hide_on_checkable_item_selection(false);
 	display_submenu->add_radio_check_item(TTR("Directional Shadow Splits"), VIEW_DISPLAY_DEBUG_PSSM_SPLITS);
 	display_submenu->add_separator();
 	display_submenu->add_radio_check_item(TTR("Normal Buffer"), VIEW_DISPLAY_NORMAL_BUFFER);