Accelerator keys (or keyboard accelerators) are keyboard shortcuts that improve the usability and accessibility of your Windows applications by providing an intuitive way for users to invoke common actions or commands without navigating the app UI. You can add them to a Button using the KeyboardAccelerators property. See the example below.
In the XAML of WinUI3 apps you can use the inline syntax for creating Rows and Columns inside a Grid. This is a feature which Avalonia had for a long time. It is more compact and works fine as long as you don't need a Max or Min Width/Height.
The following screenshot shows you a Grid with 2 Rows and Columns. Both in equal size. Using 4 Rectangle elements I created the Microsoft logo inside this Grid.
The following screenshot shows you the same Grid but now with inline RowDefinitions and ColumnDefinitions. It saves you a few lines of XAML.