You can determine the appearance and behavior of the TextBox used as the text editor by specifying the go:Part.TextEditAdornmentTemplate on your TextBlock. You can start with the default text editor template defined in Themes/Generic.xaml.
That includes turning on the TextBox.AcceptsReturn property, which defaults to false. TextBox Class (Windows.UI.Xaml.Controls) - Windows UWP applications | Microsoft Learn
For example, here’s an example I just tried:
<TextBlock Grid.Row="1" Text="{Binding Path=Data.PersonData, Mode=TwoWay}" go:Part.TextEditable="True"
TextAlignment="Left" TextWrapping="Wrap" Margin="4 4 4 2">
<go:Part.TextEditAdornmentTemplate>
<DataTemplate>
<TextBox FontFamily="{Binding Path=Node.AdornedElement.FontFamily, Mode=OneTime}"
FontSize="{Binding Path=Node.AdornedElement.FontSize, Mode=OneTime}"
FontStretch="{Binding Path=Node.AdornedElement.FontStretch, Mode=OneTime}"
FontStyle="{Binding Path=Node.AdornedElement.FontStyle, Mode=OneTime}"
FontWeight="{Binding Path=Node.AdornedElement.FontWeight, Mode=OneTime}"
TextAlignment="{Binding Path=Node.AdornedElement.TextAlignment, Mode=OneTime}"
TextDecorations="{Binding Path=Node.AdornedElement.TextDecorations, Mode=OneTime}"
TextWrapping="{Binding Path=Node.AdornedElement.TextWrapping, Mode=OneTime}"
AcceptsReturn="True"
Background="White"
Foreground="Black" />
</DataTemplate>
</go:Part.TextEditAdornmentTemplate>
</TextBlock>