Hide or collapse non-active sub-pages?

How can I customize the page widget to show a page structure like this:

Page1
– Subpage1.1
– Subpage1.2
Page 2
– Subpage 2.1
– Subpage 2.2

In this format:

Page 1 (is active)
– Subpage 1.1 (is visible)
– Subpage 1.2 (is visible)
Page 2 (same level as Page 1 – is visible)

and the Page 2 subpages are not visible.

Or, is there a widget/plugin for this? I tried Folding Pages widget and Flexi Pages widget. At some point I think I created the setup with the built-in pages widget but somehow lost the configuration… what am I missing?

Thank you!!!