That's a good point, it looks like the functions haven't been exposed in the header but they exist in the lib.
You can add the following functions to the header (or your code) if you want to use them:
void SetEffectConstantVectorElement( DWORD szName, int index, int vector );
int GetObjectEffect( int iObjID, int iLimb );
void ReleaseEffectPointer( );
and an example of how you might use it:
dbMakeVector4( 1 );
dbSetVector4( 1, 0,0,0,10 );
GetObjectEffect( 1,-1 );
SetEffectConstantVectorElement( (DWORD)"LightPos", 0, 1 );
ReleaseEffectPointer( );
dbDeleteVector4( 1 );
There's no 'db' prefix on them yet, an update to GDK may add this.