GodotTutorials/addons/custom_inspector_tools/InspectorPlugins/TestBoxAttribute.cs

using System;

namespace Tutorials.addons.custom_inspector_tools.InspectorPlugins;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class TestBoxAttribute : Attribute
{
    public string Identifier { get; }
    public string Text { get; }
    
    public TestBoxAttribute(string identifier, string text)
    {
        Identifier = identifier;
        Text = text;
    }
}