I have moved the mouse away, the pointer is not over an element of the NavigationView, but the SubPages remain visible. I would like it to be collapsed, and expand again when I move the mouse over the Page (the orange area).

Currently the built-in feature of NavViewmenu does not support highlighting the parent (root) node page. It highlights the selected page when expanded, but when collapsed, it only highlights the selected node if it is at the top level.