A Useful Extension of the Built-In Unity Coroutines.

CoroutineManager.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CoroutineManager : MonoBehaviour
{
    private static CoroutineManager _instance;
    private static CoroutineManager Instance
    {
        get
        {
            if (_instance == null)
            {
                _instance = new GameObject("Coroutine Manager").AddComponent<CoroutineManager>();
                DontDestroyOnLoad(_instance.gameObject);
            }

            return _instance;
        }
    }

    private struct ActionData
    {
        public IEnumerator coroutine;
        public bool running;
    }

    private static Dictionary<string, ActionData> map = new Dictionary<string, ActionData>();

    public static Coroutine Start(string key, IEnumerator action, bool replaceExisting = false)
    {
        if (map.ContainsKey(key))
        {
            if (replaceExisting || !map[key].running)
            {
                Stop(key);
                map.Remove(key);
            }
            else
            {
                return null;
            }
        }
        var newData = new ActionData();
        newData.coroutine = action;
        map.Add(key, newData);
        return Instance.StartCoroutine(Execute(key, action));
    }

    private static IEnumerator Execute(string key, IEnumerator action)
    {
        var data = map[key];
        data.running = true;
        map[key] = data;

        yield return action;

        data.running = false;
        map[key] = data;
    }

    public static bool IsRunning(string key)
    {
        if (!map.ContainsKey(key))
        {
            return false;
        }
        return map[key].running;
    }

    public static bool Stop(string key)
    {
        if (!map.ContainsKey(key))
        {
            return false;
        }
        Instance.StopCoroutine(map[key].coroutine);
        map.Remove(key);
        return true;
    }
}