Looks like Loadable Drawer dont work with DictionarySerialisation
[SerializeField] Dictionary<GUID, Loadable<Object>> _loadableDict;
adding item to dict cause this exception:
NullReferenceException: Object reference not set to an instance of an object
UnityEditor.LoadableDrawer.FindLoadableType (UnityEditor.SerializedProperty property) (at <1adad09540b4497e9ceb2c358d7edfba>:0)
UnityEditor.LoadableDrawer.CreatePropertyGUI (UnityEditor.SerializedProperty property) (at <1adad09540b4497e9ceb2c358d7edfba>:0)
UnityEditor.UIElements.PropertyField.ResetInternal (UnityEditor.SerializedProperty newProperty) (at <cfa9ef79539140acad1f7e6edb192abb>:0)
UnityEditor.UIElements.PropertyField.Reset (UnityEditor.SerializedProperty newProperty) (at <cfa9ef79539140acad1f7e6edb192abb>:0)
UnityEditor.UIElements.PropertyField.Reset (UnityEditor.UIElements.SerializedPropertyBindEvent evt) (at <cfa9ef79539140acad1f7e6edb192abb>:0)
UnityEditor.UIElements.PropertyField.HandleEventBubbleUp (UnityEngine.UIElements.EventBase evt) (at <cfa9ef79539140acad1f7e6edb192abb>:0)
UnityEngine.UIElements.CallbackEventHandler.HandleEventBubbleUpInternal (UnityEngine.UIElements.EventBase evt) (at <01e20fdaa89846f3a23fc6e250f14475>:0)
UnityEngine.UIElements.EventDispatchUtilities.HandleEvent_BubbleUpHandleEvent (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement element, System.Boolean disabled) (at <01e20fdaa89846f3a23fc6e250f14475>:0)
UnityEngine.UIElements.EventDispatchUtilities.HandleEventAtTargetAndDefaultPhase (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at <01e20fdaa89846f3a23fc6e250f14475>:0)
UnityEngine.UIElements.EventDispatchUtilities.SendEventDirectlyToTarget (UnityEngine.UIElements.EventBase evt, UnityEngine.UIElements.BaseVisualElementPanel panel, UnityEngine.UIElements.VisualElement target) (at <01e20fdaa89846f3a23fc6e250f14475>:0)
UnityEditor.UIElements.Bindings.SerializedObjectBindingContext.SendBindingEvent[TEventType] (TEventType evt, UnityEngine.UIElements.VisualElement target) (at <1e6a83ccc4b3453c84764f5bc153b78b>:0)
UnityEditor.UIElements.Bindings.SerializedObjectBindingContext.BindPropertyRelative (UnityEngine.UIElements.IBindable field, UnityEditor.SerializedProperty parentProperty) (at <1e6a83ccc4b3453c84764f5bc153b78b>:0)```