Если тебе нужен конструктор, то вот что написано на офф сайте
JetBrains Rider supports creating and working with Xamarin applications for both Android and iOS. Although currently JetBrains Rider does not provide a designer or a previewer for Xamarin forms, you can still benefit from code analysis, coding assistance, and debugging features in C#,
VB.NET, and other languages, as well as from general IDE features, such as the integrated VCS client.