added tooltips

com.unity.perception/Editor/Randomization/Editors/RunInUnitySimulationWindow.cs

         string m_BuildZipPath;
         SysParamDefinition[] m_SysParamDefinitions;
         IntegerField m_InstanceCountField;
-        Button m_RunButton;
+        IntegerField m_TotalIterationsField;
-        IntegerField m_TotalIterationsField;
+        ObjectField m_ScenarioConfig;
+        Button m_RunButton;
+        TextAsset scenarioConfig => (TextAsset)m_ScenarioConfig.value;
+        string scenarioConfigAssetPath => AssetDatabase.GetAssetPath(scenarioConfig);
 
         [MenuItem("Window/Run in Unity Simulation")]
         static void ShowWindow()
                     });
             }
 
-
+            m_ScenarioConfig = root.Q<ObjectField>("scenario-config");
+            m_ScenarioConfig.objectType = typeof(TextAsset);
+            var configPath = PlayerPrefs.GetString("SimWindow/scenarioConfig");
+            if (configPath != string.Empty)
+                m_ScenarioConfig.value = AssetDatabase.LoadAssetAtPath<TextAsset>(configPath);
+
             m_RunButton = root.Q<Button>("run-button");
             m_RunButton.clicked += RunInUnitySimulation;
 
             if (!StaticData.IsSubclassOfRawGeneric(typeof(UnitySimulationScenario<>), currentScenario.GetType()))
                 throw new NotSupportedException(
                     "Scenario class must be derived from UnitySimulationScenario to run in Unity Simulation");
+            if (scenarioConfig != null && Path.GetExtension(scenarioConfigAssetPath) != ".json")
+                throw new NotSupportedException(
+                    "Scenario configuration must be a JSON text asset");
         }
 
         void SetNewPlayerPreferences()
             PlayerPrefs.SetInt("SimWindow/instanceCount", m_InstanceCountField.value);
             PlayerPrefs.SetInt("SimWindow/sysParamIndex", m_SysParamIndex);
+            PlayerPrefs.SetString("SimWindow/scenarioConfig",
+                scenarioConfig != null ? scenarioConfigAssetPath : string.Empty);
         }
 
         void CreateLinuxBuildAndZip()
         List<AppParam> GenerateAppParamIds(CancellationToken token, float progressStart, float progressEnd)
         {
             var appParamIds = new List<AppParam>();
-            var configuration = JObject.Parse(currentScenario.SerializeToJson());
+            var configuration = JObject.Parse(scenarioConfig != null
+                ? File.ReadAllText(scenarioConfigAssetPath)
+                : currentScenario.SerializeToJson());
             var constants = configuration["constants"];
 
             constants["totalIterations"] = m_TotalIterationsField.value;

com.unity.perception/Editor/Randomization/Uxml/RunInUnitySimulationWindow.uxml

         <VisualElement class="sim-window__container-outer">
             <Label text="Simulation Parameters" class="sim-window__header-1"/>
             <TextField name="run-name" label="Run Name"/>
-            <editor:IntegerField name="total-iterations" label="Total Iterations"/>
-            <editor:IntegerField name="instance-count" label="Instance Count" max-value="10000"/>
-            <VisualElement class="unity-base-field">
+            <editor:IntegerField name="total-iterations" label="Total Iterations"
+                tooltip="The number of scenario iterations to execute"/>
+            <editor:IntegerField name="instance-count" label="Instance Count" max-value="10000"
+                tooltip="The number of instances to distribute the work load across"/>
+            <VisualElement class="unity-base-field"
+                           tooltip="The compute resources configuration to execute the simulation with">
+
+            <Label text="Optional Configuration" class="sim-window__header-1" style="margin-top: 10px;"/>
+            <editor:ObjectField name="scenario-config" label="Scenario JSON Config" allow-scene-object="false"
+                tooltip="Choose a JSON configuration to load during the run.
+                    You can leave this option blank to use the scenario settings currently configured in the editor."/>
+
             <VisualElement style="align-items: center;">
                 <Button name="run-button" text="Build and Run" style="margin: 10px; padding: 2 20; font-size: 13px;"/>
             </VisualElement>