It seems, every tutorial every example scripts explicitly states what font should be used for each node/arrow.
Instead, I'd like to specify default font which all arrows and nodes use only once (may at the beginning of file, or maybe separate style file sheets)
Put something like this at the top level:
node [fontname="default-node-font"];
edge [fontname="default-edge-font"];
I can't find this explicitly in the online manual (it's alluded to under https://www.graphviz.org/doc/info/lang.html#lexical-and-semantic-notes) but it's clearly documented in the man page.
