Many thanks for the ideas. Over the years, all of the solutions so far suggested have been tried except for a customised script which I shall investigate.
Steves suggestion for autotext is similar to the one I commonly use, in that I have a filed page with locally created individual graphics consisting of a line and filled circle bullets aligned and grouped. These are cut&pasted as required. Several lengths and orientations are there to minimise the need to ungroup to lengthen the line.
Embedding the lines at the graphics stage of the process is not always an option as the type of work I do which uses pictures in multiple places over several volumes - often framed in a montage of images. Many are conditional, dependent upon the product model or clients customer, and therefore callouts differ between examples of the same picture and are dependent on location in the books. Also continuing development means I receive modified pictures almost daily to maintain representative complex manuals for on-line download/viewing/embedding in the product, which often means modification to the callouts.
Normally I have used simple arrow heads for the task as these provide flexibility in that they are are easily lengthened, reshaped, flipped etc. I am being asked (told!) by a new client that he requires bulleted lines (he has them in basic manuals produced in Word and wants to maintain a consistent style). Although he appreciates the improvements FM will bring, he is still insistent that he doesnt want to change!
I was, and still am, hoping that someone in the forum has located or created the ability to add bullets instead of arrowheads to the simple line tool!
Trevor