Dears,

I made it with these steps:

Retrieving values from Retrieve Business Process Variables:

1. %(Submission Timestamps)
2. %(Submission Comments)
3. %(Submission Submitter Accounts)

Then I used this SDK script to build comments field values:

        protected override void Execute()
        {
            // Write your code here. The BoundEntryInfo property will access the entry, RASession will get the Repository Access session

            var CommentsAll=GetTokenValue("CommentsAll");
            var CommentsTime=GetTokenValue("CommentsTimeAll");
            var ActionsSubmissionAll=GetTokenValue("ActionsSubmissionAll");
            
			List<string> CommentsList=new List<string>();
          
            try
            {
                List<object> CommentsAllList = ((IEnumerable)CommentsAll).Cast<object>().ToList();
                List<object> CommentsTimeAllList = ((IEnumerable)CommentsTime).Cast<object>().ToList();
                List<object> ActionsSubmissionList = ((IEnumerable)ActionsSubmissionAll).Cast<object>().ToList();


				for (int i = 0; i < CommentsAllList.Count; i++)
                {
                    try{
                        CommentsList.Add(ActionsSubmissionList[i]+"("+CommentsTimeAllList[i].ToString()+")"+"- "+ CommentsAllList[i]);
                    }
                    catch(Exception ex1)
                    {

                    }
                }   
            }
            catch(Exception ex)
            {
              SetToken("Exception",  ex.Message);
            }

            SetToken("CommentsList",CommentsList);

        }
    }

Then I used "CommentsList" to assign value.

Thanks.