Maybe try yEd? https://www.yworks.com/products/yed
Two things I've come across. Haven't used either much, but figured I'd mention them:
I don't know about drawing, but the inference problem is one of the things probabilistic programming languages (like Church or PyMC) are designed to solve - I wonder if anyone's tried to automate the generation of a diagram from a probabilistic model.
I'm collecting my findings in a bunch of ageing-related systems. These consist of a bunch of networks with arrows pointing to things. What's making it difficult is the lack of a software to do this in. (Would need to have a system of nodes, directed arrows and those flat-headed arrows, and be reasonably user-friendly) Anyone use something like this themselves?