If you have a Discount item that you have set up in your Point of Sale and do not see it in Shogo - then that discount has not been used in a sale (at least from your Shogo start date). Shogo only recognizes items after they have been used.
If you have defined QuickBooks items that you do not see in Shogo, you can refresh reference data in Shogo to see these.
You can have specific Discounts or categories in your Point of Sale for example
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If you want to see these type of items or categories and do not, it is because you have used the "All Discounts" default mapping in your Shogo accounting mapping.
If the "All Discounts" line item is mapped, then any Discount that does not have its own mapping (e.g. is set to None) will use the mapping from the All Discounts setting.
This will cause your Discount categories to be lumped together into one entry and you will loose the level of detail you want.