An Unity editor script to help navigating in hierarchy or project browser

SelectionHistory.cs

using System.Collections.Generic;
using System.Linq;
using UnityEditor;
using UnityEngine;

[InitializeOnLoad]
public class SelectionHistory
{
	private const int MAX_HISTORY_COUNT = 10;

	public static SelectionHistory Instance { get; private set; }

	private bool skipRecord;
	private SelectionSnapshot currentState;
	private HistoryStack<SelectionSnapshot> back, forward;

	static SelectionHistory()
	{
		Instance = new SelectionHistory();
		Instance.Start();
	}

	private void Start()
	{
		currentState = TakeSnapshot();
		back = new HistoryStack<SelectionSnapshot>(MAX_HISTORY_COUNT);
		forward = new HistoryStack<SelectionSnapshot>(MAX_HISTORY_COUNT);
		Selection.selectionChanged += OnSelectionChanged;
	}

	private void OnSelectionChanged()
	{
		// skip back or forward changes
		if (skipRecord)
		{
			skipRecord = false;
		}
		else
		{
			RecordSelection();
		}

		currentState = TakeSnapshot();
	}

	[MenuItem("Selection / Back _[")]
	private static void MenuItemBack()
	{
		Instance.Back();
	}

	[MenuItem("Selection / Forward _]")]
	private static void MenuItemForward()
	{
		Instance.Forward();
	}

	private void RecordSelection()
	{
		// do not record empty entry
		if (IsDeselected())
		{
			return;
		}

		// do not record same entry
		SelectionSnapshot latestHistory = back.Peek();
		if (latestHistory != null
		    && latestHistory.ActiveObject == currentState.ActiveObject
		    && latestHistory.Objects.SequenceEqual(currentState.Objects))
		{
			return;
		}

		back.Push(currentState);
		forward.Clear();
	}

	private void Back()
	{
		if (back.Count == 0)
		{
			return;
		}

		// prevent forward to null
		if (!IsDeselected())
		{
			forward.Push(currentState);
		}

		SelectionSnapshot snapshot = back.Pop();
		RestoreSnapshot(snapshot);
	}

	private void Forward()
	{
		if (forward.Count == 0)
		{
			return;
		}

		back.Push(currentState);
		SelectionSnapshot snapshot = forward.Pop();
		RestoreSnapshot(snapshot);
	}

	private SelectionSnapshot TakeSnapshot()
	{
		return new SelectionSnapshot
		{
			Window = EditorWindow.focusedWindow,
			ActiveObject = Selection.activeObject,
			Objects = Selection.objects
		};
	}

	private void RestoreSnapshot(SelectionSnapshot snapshot)
	{
		skipRecord = true;
		Selection.activeObject = snapshot.ActiveObject;
		Selection.objects = snapshot.Objects;
		snapshot.Window.Focus(); // TODO handle locked ProjectBrowser
		EditorGUIUtility.PingObject(snapshot.ActiveObject);
	}

	private bool IsDeselected()
	{
		return currentState == null || currentState.ActiveObject == null;
	}
}

public class HistoryStack<T>
{
	private readonly int size;
	private readonly LinkedList<T> collection;

	public HistoryStack(int size)
	{
		this.size = size;
		collection = new LinkedList<T>();
	}

	public void Push(T snapshot)
	{
		collection.AddLast(snapshot);

		// remove too old records
		while (collection.Count > size)
		{
			collection.RemoveFirst();
		}
	}

	public T Pop()
	{
		T snapshot = collection.Last.Value;
		collection.RemoveLast();
		return snapshot;
	}

	public T Peek()
	{
		return collection.Count == 0 ? default : collection.Last.Value;
	}

	public void Clear()
	{
		collection.Clear();
	}

	public int Count => collection.Count;
}

public class SelectionSnapshot
{
	public EditorWindow Window;
	public Object ActiveObject;
	public Object[] Objects;
}