1970's TV episode titles on crew credits

As a DGA trainee assistant director, I worked multiple episodes on several TV series in the early 70's.  I'm trying to make a simple adjustment to the way my job is currently listed for that period (i.e., change "dga trainee" to "DGA trainee").  I know how to do this, and have done so on my non-episodic credits.  But when I try to make this adjustment on series credits, the change is rejected because I haven't specified the titles of specific episodes on which I worked.  IMDb now provides a list of episodes from which to choose, but we're talking 47-48 years ago -- who can remember?  Anyone have a suggestion for how to accomplish my mission without naming episodes?