User can choose their base directory

com.unity.perception/Editor/GroundTruth/PerceptionCameraEditor.cs

 using System;
 using System.Collections.Generic;
+using System.IO;
 using UnityEditorInternal;
 using UnityEngine;
 using UnityEngine.Perception.GroundTruth;
                 GUILayout.BeginVertical("TextArea");
                 EditorGUILayout.HelpBox(dir, MessageType.None);
                 GUILayout.BeginHorizontal();
+                if (GUILayout.Button("Choose Base Folder"))
+                {
+                    var path = EditorUtility.OpenFolderPanel("Choose Base Folder", "", "");
+                    if (path.Length != 0)
+                    {
+                        Debug.Log($"Chose path: {path}");
+                        PlayerPrefs.SetString(SimulationState.userBaseDirectoryKey, path);
+                        PlayerPrefs.SetString(SimulationState.latestOutputDirectoryKey, path);
+                        perceptionCamera.baseDirectory = path;
+                    }
+                }
                 if (GUILayout.Button("Show Folder"))
                 {
                     EditorUtility.RevealInFinder(dir);

com.unity.perception/Runtime/GroundTruth/SimulationState.cs

         float m_LastTimeScale;
         readonly string m_OutputDirectoryName;
         string m_OutputDirectoryPath;
+        public const string userBaseDirectoryKey = "userBaseDirectory";
         public const string latestOutputDirectoryKey = "latestOutputDirectory";
 
         public bool IsRunning { get; private set; }
         public SimulationState(string outputDirectory)
         {
             m_OutputDirectoryName = outputDirectory;
-            PlayerPrefs.SetString(latestOutputDirectoryKey, Manager.Instance.GetDirectoryFor());
+            var basePath = PlayerPrefs.GetString(userBaseDirectoryKey, string.Empty);
+
+            if (basePath != string.Empty)
+            {
+                if (Directory.Exists(basePath))
+                {
+                    Configuration.localPersistentDataPath = basePath;
+                }
+                else
+                {
+                    Debug.LogWarning($"Passed in directory to store simulation artifacts: {basePath}, does not exist. Using default directory {Configuration.localPersistentDataPath} instead.");
+                    basePath = Configuration.localPersistentDataPath;
+                }
+            }
+
+            PlayerPrefs.SetString(latestOutputDirectoryKey, Manager.Instance.GetDirectoryFor("", basePath));
             IsRunning = true;
         }