Add Button next to "toggle sidebar" button in NavigationSplitView

Hi, I am trying to add a custom (create) button next to the automatic "toggle sidebar" button in a NavigationSplitView.

When the sidebar is collapsed that button should be displayed in a group with that automatic toggle button.

Basically I want exact the same behaviour as in the Apple "Reminders" App.

How could I archive that?

Thanks for your help :-)

Jan

Add Button next to "toggle sidebar" button in NavigationSplitView
 
 
Q