GodotTutorials/addons/custom_inspector_tools/CustomInspectorPlugin.cs

using System;
using System.Collections.Generic;
using Godot;
using Tutorials.addons.custom_inspector_tools.InspectorPlugins;

namespace Tutorials.addons.custom_inspector_tools;

#if TOOLS
[Tool]
public partial class CustomInspectorPlugin : EditorPlugin
{
    private readonly List<EditorInspectorPlugin> _customPlugins = new();
    private bool _pluginsBuilt = false;
    private bool _inspectorPluginsAdded = false;

    private EditorSelection _selection;
    private bool _refreshingInspector = false;
    
    public override void _EnterTree()
    {
        base._EnterTree();

        if (!_pluginsBuilt)
        {
            BuildPlugins();
            _pluginsBuilt = true;
        }

        _selection = EditorInterface.Singleton.GetSelection();
        _selection.SelectionChanged += OnSelectionChanged;
    }

    private void OnSelectionChanged()
    {
        if (!_inspectorPluginsAdded)
        {
            return;
        }


        RefreshInspectorForCurrentSelection();
    }

    private void RefreshInspectorForCurrentSelection()
    {
        if (_refreshingInspector)
        {
            return;
        }

        _refreshingInspector = true;

        try
        {
            GodotObject objToInspect = null;
            
            foreach (var node in _selection.GetSelectedNodes())
            {
                if (node is not null)
                {
                    objToInspect = node;
                    break;
                }
            }
            
            // Drop old inspector UI, then rebuild for the selected object.
            EditorInterface.Singleton.InspectObject(null);
            
            if (objToInspect is not null)
            {
                EditorInterface.Singleton.InspectObject(objToInspect);
            }
        }
        finally
        {
            _refreshingInspector = false;
        }
    }

    private void BuildPlugins()
    {
        _customPlugins.Clear();
        
        // Add new plugins here as you create them.
        _customPlugins.Add(new TestBoxInspectorPlugin());
    }

    public override void _EnablePlugin()
    {
        base._EnablePlugin();

        try
        {
            if (_inspectorPluginsAdded)
                return;

            foreach (var plugin in _customPlugins)
            {
                AddInspectorPlugin(plugin);
                GD.Print($"Added inspector plugin: {plugin.GetType().Name}");
            }

            _inspectorPluginsAdded = true;

            RefreshInspectorForCurrentSelection();
        }
        catch (Exception ex)
        {
            GD.PrintErr($"Error enabling CustomInspectorPlugin: {ex.Message}");
        }
    }

    public override void _DisablePlugin()
    {
        try
        {
            RemoveAllInspectorPlugins();

            EditorInterface.Singleton.InspectObject(null);
            RefreshInspectorForCurrentSelection();
        }
        catch (Exception ex)
        {
            GD.PrintErr($"Error disabling CustomInspectorPlugin: {ex.Message}");
        }
        base._DisablePlugin();
    }

    private void RemoveAllInspectorPlugins()
    {
        if (!_inspectorPluginsAdded)
            return;

        foreach (var plugin in _customPlugins)
        {
            RemoveInspectorPlugin(plugin);
            GD.Print($"Removed inspector plugin: {plugin.GetType().Name}");
        }

        _inspectorPluginsAdded = false;
    }
}
#endif