In the Layout Side Menu, more often the end user prefer a menu is kept open while one of its submenu is clicked.
This sample shows how to keep menu open where the menu is dynamically generated from entity data.
Here are some forums to address this issue:
https://www.outsystems.com/forums/discussion/98182/how-to-keep-menu-open-when-its-submenu-is-clicked-in-a-dynamic-menu/