How to create a fixed region sidebar without affecting the widget in the sidebar?

I have a sidebar which contains a lot of dropdown menu. I want to let the sidebar to be fixed even if we are scrolling the page to the bottom, we still can see the same sidebar. I have tried to assign some custom css such as position: fixed; in the sidebar. However, it will affect the dropdown menu.  
1 answers

looks like you need some advanced layouts.

Maui9 supports this.