private void AddPlaylistToList(string playlistURL)
        {
            string playlistID = Regex.Match(playlistURL, @"(PL|UU|UC)[\w-]*").Value;

            if (playlistID.StartsWith("UC"))
            {
                playlistID = playlistID.Replace("UC", "UU");
            }
            else if (playlistURL.Contains("/user/"))
            {
                playlistID = GetChannelId(playlistURL).Replace("UC", "UU");
            }

            if (string.IsNullOrEmpty(playlistID))
            {
                MessageBox.Show($"Could not find a playlist ID for {playlistURL}");
                return;
            }

            Subscription playlistSubscription = YouTubeFunctions.GetPlaylistAsSubscription(playlistID);

            playlistSubscription.FilterRegex = textBoxRegex.Text;

            Add(playlistSubscription);
        }