Unity Editor extension to generate unique identifiers for strings. Shows a 'Generate' button next to a string input field in the inspector, for any string property where a [UID] attribute is assigned. For example: [UID] public string id;

UIDAttribute.cs

using UnityEngine;

// Example usage:
// [UID] public string id;
public class UIDAttribute : PropertyAttribute
{

}

UIDAttributeDrawer.cs

using UnityEngine;
using UnityEditor;
using System;

[CustomPropertyDrawer(typeof(UIDAttribute))]
public class UIDAttributeDrawer : PropertyDrawer
{

	public override void OnGUI(Rect position, SerializedProperty property, GUIContent label)
	{
		//UIDAttribute range = attribute as UIDAttribute;

		if (property.propertyType == SerializedPropertyType.String) {
			Rect idRect = new Rect (position.x, position.y, position.width-70, EditorGUIUtility.singleLineHeight);
			Rect buttonRect = new Rect (position.x+(position.width-70), position.y, 70, EditorGUIUtility.singleLineHeight);

			EditorGUI.PropertyField (idRect, property);
			if (GUI.Button (buttonRect, "Generate")) {
				property.stringValue = Generate(false,true,true);
			}
		} else
			EditorGUI.LabelField(position, label.text, "Use UID with string values");
	}

	private string Generate(bool getSecondsNotTicks, bool getMillisecondsNotTicks, bool getHexValue)
	{
		string id = string.Empty;

		DateTime historicalDate = new DateTime(1970, 1, 1, 0, 0, 0);

		if (getSecondsNotTicks || getMillisecondsNotTicks)
		{
			TimeSpan spanTillNow = DateTime.UtcNow.Subtract(historicalDate);

			if (getSecondsNotTicks)
				id = String.Format("{0:0}", spanTillNow.TotalSeconds);
			else
				id = String.Format("{0:0}", spanTillNow.TotalMilliseconds);
		}
		else
		{
			long ticksTillNow = DateTime.UtcNow.Ticks - historicalDate.Ticks;
			id = ticksTillNow.ToString();
		}

		if (getHexValue)
			id = long.Parse(id).ToString("X");

		return id;
	}

}