Hi, I use following code:
<inputLayout:SfTextInputLayout Grid.Row="1" Grid.Column="1" Hint="Bemerkung" Margin="0,20,0,0" FocusedColor="{StaticResource PrimaryColor}" ReserveSpaceForAssistiveLabels="False" >
<Editor Text="{Binding Note, Mode=TwoWay}" IsSpellCheckEnabled="True" IsTextPredictionEnabled="True" AutoSize="TextChanges" Style="{StaticResource DefaultEditorStyle}"/>
</inputLayout:SfTextInputLayout>
When the Editor control grows, the Hint move from the top to the middle of the control. This happens on iOS and Android. UWP work OK. I use the 17.3.0.33 Version.