Originally written by @codepoet, then maintained for a while by @Papa_Joe, this is another fuel-balancing mod. Original thread is here: https://forum.kerbalspaceprogram.com/index.php?/topic/39263-105-p, second thread is here: https://forum.kerbalspaceprogram.com/index.php?/topic/147144-113-pwb-fuel-balance
After numerous attempts to contact @Papa_Joe, I've adopted this mod and made some improvements
What is PWB Fuel Balancer?
Mod to automatically move fuel between tanks to