There are some tricks that you can try, listed below. The layouting itself is performed by GraphViz (dot layouting iirc), and GraphViz simply does this sometimes. Graph layouting is a NP-complete problem, so algorithms usually take harsh shortcuts.
Typical workarounds that I’ve seen or used include:
- adding hidden lines
a -[hidden]- b - extending the length of a line
a --- b(more dashes, longer line) - specifying preferred direction of lines (
a -left- b) - swapping association ends (
a -- b→b -- a) - changing the order of definitions (the order does matter… sometimes)
- adding empty nodes with background/border colors set to Transparent
So if you really want to have a nice layout, you’ll need to put some elbow grease in, but keep in mind that the layout will be still brittle — if you add/remove items, you might need to redo it again.