Added the project.

Assets/TubeLight/Editor/TubeLightEditor.cs

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+using UnityEngine;
+using UnityEditor;
+using UnityEditor.AnimatedValues;
+
+[CustomEditor(typeof(TubeLight))]
+[CanEditMultipleObjects]
+public class TubeLightEditor : Editor {
+
+	AnimFloat m_ShowInfo;
+
+	void OnEnable()
+	{
+		m_ShowInfo = new AnimFloat(0);
+		m_ShowInfo.valueChanged.AddListener(Repaint);
+		m_ShowInfo.speed = 0.5f;
+	}
+
+	override public void OnInspectorGUI()
+	{
+		DrawDefaultInspector();
+
+		if (targets.Length > 1)
+			return;
+
+		EditorGUILayout.Space();
+
+		if(GUILayout.Button("Add a shadow plane"))
+			m_ShowInfo.value = AddShadowPlane() ? 0 : 100;
+
+		foreach (TubeLightShadowPlane shadowPlane in ((TubeLight)target).m_ShadowPlanes)
+			if (shadowPlane != null)
+				EditorGUILayout.ObjectField("Shadow Plane", shadowPlane, typeof(TubeLightShadowPlane), !EditorUtility.IsPersistent(target));
+
+		m_ShowInfo.target = 0;
+		if (EditorGUILayout.BeginFadeGroup(Mathf.Min(1.0f, m_ShowInfo.value)))
+			EditorGUILayout.HelpBox("Limit of " + TubeLight.maxPlanes + " planes reached. Delete an existing one.", MessageType.Info);
+		EditorGUILayout.EndFadeGroup();
+	}
+
+	bool AddShadowPlane()
+	{
+		TubeLight tubeLight = (TubeLight)target;
+
+		int i = 0;
+		for (; i < TubeLight.maxPlanes; i++)
+		{
+			if (tubeLight.m_ShadowPlanes[i] != null)
+				continue;
+			
+			GameObject go = new GameObject("Shadow Plane");
+			TubeLightShadowPlane shadowPlane = go.AddComponent<TubeLightShadowPlane>();
+
+			go.transform.position = tubeLight.transform.position + go.transform.forward;
+			go.transform.parent = tubeLight.transform;
+			tubeLight.m_ShadowPlanes[i] = shadowPlane;
+			EditorUtility.SetDirty (tubeLight);
+			break;
+		}
+
+		return i < TubeLight.maxPlanes;
+	}
+}

Assets/TubeLight/Editor/TubeLightEditor.cs.meta

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+timeCreated: 1446582855
+licenseType: Pro
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+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
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