setx
Permanently set an environment variable — unlike set, it persists after the window closes.
setx MYVAR "value"
/m set for all users (needs admin)
Practice line — try it from memory, then reveal
setx MYVAR "value"
Try it safely
Run setx MYVAR "value" in the practice shell →
Chapter 13: Runes of the Realm. A sandboxed Command Prompt; nothing touches your PC.