Is there a list where I can look for the values for the AppBarButtons?
If I’m looking in the StandardLayout.xaml I found some examples, like this
<Style x:Key="ZoomOutButtonStyle" TargetType="Button" BasedOn="{StaticResource AppBarButtonStyle}">
<Setter Property="AutomationProperties.AutomationId" Value="ZoomOutButtonStyle"/>
<Setter Property="AutomationProperties.Name" Value="Zoom Out"/>
<Setter Property="Content" Value=""/>
</Style>
Is there a list for the values like

Thanks.
Run the Character Map program & select the Segoe UI Symbol from the font list:-
the bit you are looking for, in your example is,  just ignore the &#x at the beginning. You can use any font viewer program or check out the free version of Syncfusion Metro Studio (2 intro min vid) at Syncfusion Metro Studio FREE for more advanced icon manipulation.
Just have fun trying…