I want to show the Resize Button in Notification Panel But did not find a way

That is set in the Sidebar properties. To view that, you'll need to view the Page settings, click the three-dot button on the top right, then select "Page settings". On that panel you'll see a button for "Manage sidebar parameters". There's an option for that there.

Ryan

Ryan Farley,

Hello Ryan , 

This is what I get :

Astro Developer,

Since you appear to be modifying the out of the box Chats panel, it could be that this sidebar possibly has that bound to an attribute, making it not enabled (there is a page Parameter for AllowSizeAdjustment for sidebars) or maybe it uses a different base page type?