Code:
/run SetCVar("graphicsComputeEffects", x)
with x in {0, ..., 4} works for me.
But your Graphics panel will not show another value until all cvars match.
The "Compute Effects" UI switch does not just control the cvar graphicsComputeEffects but others too like volumeFogLevel, particulatesEnabled or volumeFog. You can check this by tracking your Config.wtf file while you change settings.