I realize this is an older post, but wanted to contribute to the discussion as I have recently dealt with improving a process map within my company's QMS. Attached is what I came up with and was well-received by my supervisor. The entire point was to illustrate process interaction between each department and related procedures. Each procedure box is linked to the high-level written procedure (I've removed those on this attachment, but you get the idea). Within the each of the written procedures, sub-procedures / work instructions / forms / etc. are linked as well.