Global modifiers are useful when you want to make a change across all your shipping rates but do not want to modify all your rates individually. They are particularly handy when you need to apply a temporary markup or reduction on your rates.
Acme Inc. wants to offer 50% off all shipping rates when a customer spends over $30 during the week leading up to Mothers Day. They have a complex shipping setup with several Regions and a fairly large number of Rates.
Rather than update all their rates, ACME Inc. create a global modifier that:
Reduces the price of shipping rates by 50%
Appends a note to the rate description - “Half price shipping on orders over $30!”
Has a rule that ensures that the modifier will only be applied if the total order value is over $30
Set temporary (or long-term) modifications on your shipping rates.
Increase or decrease the rate price by a fixed amount or a percentage of the rate price.
Modify or replace the existing rate description.
Set rules that govern when the modifier should be applied.