Since the standard Blades in the Dark system hasn't been updated in a couple of major Foundry verseions and is not v12-compatible, this update of my custom sheets requires a separate BitD system to be manually installed: https://github.com/Dez384/foundryvtt-blades-in-the-dark
System manifest link here:
https://raw.githubusercontent.com/Dez384/foundryvtt-blades-in-the-dark/master/system.json