If I set Time Scale to 0, Wait for x sec Doesn't Work

Is there another countdown system?

You can set an object, or families time scale separate from the system timescale.

What I usually do is just set a variable on a sprite, set time scale 0 and object time scale to 1 and then count that number down 1 every tick. I then do a check if the variable is less or equal to 0, then you can call whatever you would after your "wait" command. It's kind a of a pain, but the only way I've figured it out to work.

The wallclocktime system expression always advances at the normal rate regardless of any other time scaling.