MissingMethodException: void

Unity Engine
,
6

Thanks @b4gn0 ! That is great to know. I do have the UI Toolkit 1.0.0-preview.9 installed and will try 2020.2.0b1.

Edit: Sadly, with 2020.2.0b1, the editor repeatedly (forever) asks me to use the default layout, while failing with this error:

[LAYOUT] About to load Library/CurrentLayout-default.dwlt, keepMainWindow=False
Failed to load window layout: System.NullReferenceException: Object reference not set to an instance of an object
  at UnityEditor.ContainerWindow.GetWindowID () [0x0006a] in /Users/bokken/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:339
  at UnityEditor.ContainerWindow.get_windowID () [0x00010] in /Users/bokken/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:81
  at UnityEditor.ContainerWindow.SaveGeometry () [0x00001] in /Users/bokken/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:363
  at UnityEditor.ContainerWindow.Save () [0x0000d] in /Users/bokken/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:378
  at UnityEditor.ContainerWindow.Close () [0x00001] in /Users/bokken/buildslave/unity/build/Editor/Mono/ContainerWindow.cs:310
  at UnityEditor.WindowLayout.LoadWindowLayout (System.String path, System.Boolean newProjectLayoutWasCreated, System.Boolean setLastLoadedLayoutName, System.Boolean keepMainWindow) [0x000db] in /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/WindowLayout.cs:1020
#0 GetStacktrace(int)
#1 DebugStringToFile(DebugStringToFileData const&)
#2 DebugLogHandler::Internal_Log(LogType, LogOption, core::basic_string<char, core::StringStorageDefault<char> >, Object*)
#3 DebugLogHandler_CUSTOM_Internal_Log(LogType, LogOption, ScriptingBackendNativeStringPtrOpaque*, ScriptingBackendNativeObjectPtrOpaque*)
#4  (Mono JIT Code) (wrapper managed-to-native) UnityEngine.DebugLogHandler:Internal_Log (UnityEngine.LogType,UnityEngine.LogOption,string,UnityEngine.Object)
#5  (Mono JIT Code) [WindowLayout.cs:983] UnityEditor.WindowLayout:LoadWindowLayout (string,bool)
#6  (Mono JIT Code) [WindowLayout.cs:338] UnityEditor.WindowLayout:LoadProjectLayout (bool)

Edit 2: First moving to e.g. b8, then back to b1 works to overcome the editor loading issue.