We are not sure that we fully understand what you have in mind. We cannot understand if your question is related with the XamarinForms NavigationPage or it is related to the RadSideDrawer component of our UI for Xamarin suite.
Basically, the RadSideDrawer exposes the IsOpened property. It allows users to open or close the drawer when it is needed from code. On the other hand, the NavigationPage toolbar button exposes click event handler which allows programmers to detect when the end user has clicked/tapped on the button. At the end, the combination of these two APIs should allow you to easily open and close the RadSideDrawer from a dedicated navigation page button.
However, if we misunderstood you and this is not the required behavior, please provide us with more detailed information about it. Maybe some sketches or drawings will help us understand you.
I hope this information is helpful.
Pavel R. Pavlov
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