Extension to easily add/remove custom defines to specific build targets

CustomDefineEditor.cs

using UnityEditor;
using UnityEngine;

namespace Utils
{

	public class CustomDefineEditor : EditorWindow
	{

		private string[] defines =
		{
			"debug"
		};

		private bool[] values;
		private BuildTargetGroup selectedTargetGroup;

		private void Awake()
		{
			values = new bool[defines.Length];
			selectedTargetGroup = EditorUserBuildSettings.selectedBuildTargetGroup;
			LoadCustomDefines();
		}

		[MenuItem("Window/CustomDefines")]
		public static void ShowWindow()
		{
			EditorWindow.GetWindow(typeof(CustomDefineEditor), false, "CustomDefines");
		}

		private void OnGUI()
		{

			GUILayout.Label("Target", EditorStyles.boldLabel);
			BuildTargetGroup selection = (BuildTargetGroup)EditorGUILayout.EnumPopup("Selected target", selectedTargetGroup);
			if (selection != selectedTargetGroup)
			{
				selectedTargetGroup = selection;
				LoadCustomDefines();
			}

			GUILayout.Label("Defines", EditorStyles.boldLabel);
			for (int i = 0; i < defines.Length; i++)
			{
				string define = defines[i];
				values[i] = EditorGUILayout.Toggle(define, values[i]);
			}

			if (GUILayout.Button("Save"))
			{
				SaveCustomDefines();
				Debug.Log("Custom defines saved!");
			}

		}

		private void SaveCustomDefines()
		{
			string definesToSave = "";

			for (int i = 0; i < values.Length; i++)
			{
				if (values[i])
				{
					definesToSave += defines[i] + ";";
				}
			}

			PlayerSettings.SetScriptingDefineSymbolsForGroup(selectedTargetGroup, definesToSave);
		}

		private void LoadCustomDefines()
		{
			string customDefines = PlayerSettings.GetScriptingDefineSymbolsForGroup(selectedTargetGroup);

			for (int i = 0; i < defines.Length; i++)
			{
				values[i] = customDefines.Contains(defines[i]);
			}
		}

	}

}