Do missing bags affect W&B
 

With the news covering QF being the safest airline, but at the same covering bags missing flights etc,
do missing bags affect W&B issues with multiple bags missing? If so, how could this be a safe operation if it affects W&B?

One of the design aspects of loading systems (ie how to figure weight and balance for a flight) is to embody tolerance checks so that minor errors in practice (in this case, a "wrong" baggage value) are covered by the tolerance flexibility of the loading system. There is a penalty in that the system, itself, will now have inbuilt errors but we can balance one against the other to end up with a useful, load error tolerant system. End result is that a few bags left behind will not create a significant hazard.

If we didn't go this way, it might be necessary to redo the sums for every change prior to flight. Not too much of a problem for a C172 but can be a real nuisance on an airline B747 operation.

Barely.

Need to take 30 hand baggage cases from the gate because the flight is full? Voila your plane now weighs an extra tonne as we pretend they’re full cases. The tolerances are so bewilderingly massive for the very reason that stuff like this happens. It allows for mucking about and trivia to take place without actually having a meaningful impact on safety.

The tolerances are so bewilderingly massive for the very reason that stuff like this happens

Methinks you need to do a little homework study because whatever training you have had in weight control and certification is shown up to be sadly lacking by that comment. A few kilos isn't going to be a showstopper - one is far more concerned about the cg. Quite apart from the engineering concerns, there is the legal concerns should you be called upon to justify whatever shortcuts you may have chosen to implement or accept.

If a sensible analysis has gone into the loading system, particularly if there are LMC adjustments, and provided it is applied correctly, fine. Otherwise, you could find yourself with a cg problem without too much difficulty, obviously depending on where things are put in or left off and weights involved.

Missing bags = not flying with the associated passenger ( hence they’re “missing”).
The missing are obviously not loaded so they won’t show up in the final load sheet.

.. so they won’t show up in the final load sheet.

Hence the necessity of a sensible curtailment analysis in the loading system design and, generally, overlaid LMC allowances.