BML or Black_dog's Modding Library is a mod I will be using as the core for my mods going forward. It contains logic and utils that can ease my devloping of mods.
Read this if you get crashes when depending on BML and trying to launch in-dev.
As a workaround, disable refmaps by defining the mixin.env.disableRefMap
JVM argument to true.
Using this under both the client and server run config
// Disable mixin refmaps
property 'mixin.env.disableRefMap', 'true'