How to reproduce:
# Open the attached package
# Open System.vfx
# Drag and drop Subgraph.vfx to System.vfx

Notes: Stacktrace looks unfamiliar, though I wasn't able to reproduce the crash by drag and dropping Subgraph to the Shadergraph

Few lines from the stacktrace:

0x00007FF9CFDEF5D1 (Unity) SerializableManagedRef::GetScriptType
0x00007FF9CFD5B432 (Unity) ThreadAndSerializationSafeCheck::ReportError
0x00007FF9CF5049C1 (Unity) EditorApplication_Get_Custom_PropIsPlaying
0x000001F9AE348057 (Mono JIT Code) (wrapper managed-to-native) UnityEditor.EditorApplication:get_isPlaying ()
0x000001F9AE347FAB (Mono JIT Code) [PackageCache\com.unity.inputsystem@1.4.2\InputSystem\NativeInputRuntime.cs:278] UnityEngine.InputSystem.LowLevel.NativeInputRuntime:get_isInPlayMode () 
0x000001F9B8F8E359 (Mono JIT Code) [PackageCache\com.unity.inputsystem@1.4.2\InputSystem\InputManager.cs:252] UnityEngine.InputSystem.InputManager:get_gameIsPlaying () 
0x000001F9ABFB2473 (Mono JIT Code) [PackageCache\com.unity.inputsystem@1.4.2\InputSystem\InputManager.cs:2746] UnityEngine.InputSystem.InputManager:ShouldRunUpdate (UnityEngine.InputSystem.LowLevel.InputUpdateType) 
0x000001F9ABFB2405 (Mono JIT Code) [PackageCache\com.unity.inputsystem@1.4.2\InputSystem\NativeInputRuntime.cs:118] UnityEngine.InputSystem.LowLevel.NativeInputRuntime/<>c_{_}DisplayClass13_0:<set_onShouldRunUpdate>b{_}_0 (UnityEngineInternal.Input.NativeInputUpdateType) 
0x000001F9ABFB228C (Mono JIT Code) UnityEngineInternal.Input.NativeInputSystem:ShouldRunUpdate (UnityEngineInternal.Input.NativeInputUpdateType,bool&)