It looks fine on the face of it and should work on steel path, tell me are you letting the glaive detonate on its own or triggering your own detonation? the regular explosion from volatile quick return won’t proc the slash as its not a heavy detonation.

You need to trigger it by performing a heavy attack while the glaive is in mid air (remapping heavy attacks to their own key helps, I like to use ‘T’), you can also heavy detonate it directly after the detonation triggered by the mod to get the benefit of both explosions.