Custom multi-tag for Unity

DynamicTag.cs

[DisallowMultipleComponent]
public class DynamicTag : MonoBehaviour
{
    private static Dictionary<string, List<GameObject>> Collection = new Dictionary<string, List<GameObject>>();

    private static string KeyFromTag(DynamicTagItem tag) {
        return tag.name;
    }

    public static void Register(DynamicTagItem tag, GameObject item) {

        var key = KeyFromTag(tag);

        if (!Collection.ContainsKey(key))
            Collection.Add(key, new List<GameObject>());

        Collection[key].Add(item);
    }

    public static void Deregister(DynamicTagItem tag, GameObject item) {

        var key = KeyFromTag(tag);

        if (!Collection.ContainsKey(key))
            return; // No Such Tag

        // In case of multiple entries, remove all occurences of item
        // If you're sure you will only have one entry per item, you can just use 'Remove'
        Collection[key].RemoveAll(m => m == item);

    }

    public static IEnumerable<GameObject> FindObjectsWithTag(DynamicTagItem tag) {
        
        var key = KeyFromTag(tag);

        if (!Collection.ContainsKey(key))
            return null;

        return Collection[key].AsEnumerable();
    }


    public DynamicTagItem[] Tags;

    private void Awake() {
        foreach (var tag in Tags)
            Register(tag, gameObject);
    }

    private void OnDestroy() {
        foreach ( var tag in Tags)
            Deregister(tag, gameObject);
    }
}

DynamicTagItem.cs

[CreateAssetMenu(fileName ="DynamicTag", menuName ="Scriptables/CustomTag")]
public class DynamicTagItem : ScriptableObject { }