One tiny shortcoming: Cyclic graph cannot be create (view is ok) on iOS platform but can be done on other platforms. Acyclic is a given.
One great feature is when it gets too big, graft-and-paste to a separate document is available.
Collaboration between devices of same account is excellent.
Disclaimer: not affiliated with XMind.
Some graph example on malware, anti-virus, and Trojans not created by me: https://www.xmind.net/m/VipY/
I did a research recently and settled with xmind but I don't really like it.
I'm definitely gonna try whiscal.
That was so close (to supporting all major platforms). XMind can do it all.