Consider following code:
MyEntry.Completed += (object sender, EventArgs e) => MyEditor.Focus();
When onscreen keyboard return button hit in MyEntry, MyEditor gets focused and new empty line is inserted to MyEditor's text. It's a well known iOS issue, it needs just UITextField.ShouldReturn to return true instead of false.
Created attachment 13792 [details]
Should be fixed in 2.3.4-pre2. Thank you!
I have checked this issue with Xamarin.Forms 2.3.4-pre1 and observed that this issue has been fixed.
Hence closing this issue.