Apologies if this is a complete newbie question, but as others have noted, I find the OmniGraffle doc/Help a little lacking in detail in places.

Is it possible to attach a magnet (or its equivalent) to a line, as well as to a shape? I do a lot of flowcharting, and often need to have flows from multiple places join a "main line" along its length, so they all converge at a single target via the single main line (making any sense?). Ideally I would like to attach magnets along the main line as endpoints for the other lines, so that as the whole thing get moved around all the attachments are retained.