Hello Andy,
Yes this is peculiar of SNP, not only in Optimiser but also in Heuristic. The Safety Days supply which is specified is for the product location and there no setting similar to " safety time indicator" as in ECC to control the supply elements.
In past we had a similar requirement from one of our clients, we proposed them to choose from the below two options,
1. Every month/Quarter/Year calculate the proportion of distribution demand to the Forecast demand at the manufacturing locations and adjust (lower) the safety days of supply for the manufacturing location by that factor with respect to what was the original target. This is a simple and practical approach.
2. Since SNP optimiser finally considers the safety stock key figure calculated via macro in the planing book, adjust the macro to do custom safety stock calculations by looking at the location type.
Fortunately, for us client accepted the first proposal with a automation program to update the safety days value in product master, we didn't get to experiment on the other suggestion. I think that also might work.
you can have a look at Restrict SNP safety stock planning scope | SCN for more pointers towards the macro adjustment.
Global Safety Stock Fallback Value is used in SSP not sure if it might help in SNP optimiser engine.
Regards,
Abhishek Rai