Make sure WalletCommands is not responsible to create the WalletManagerViewModel
ADD
WalletWasabi.Gui/Extensions/AvaloniaExtensions.cs
+using System;
+using System.Linq;
+using System.Collections.Generic;
+using System.Text;
+using AvalonStudio.Shell;
+using Avalonia.Controls;
+
+namespace System
+{
+ public static class AvaloniaExtensions
+ {
+ public static T GetDocument<T>(this IShell shell)
+ {
+ return shell.Documents.OfType<T>().Single();
+ }
+ }
+}

Make sure WalletCommands is not responsible to create the WalletManagerViewModel