From Sales open the Price lists tab and press New list. Give it a name, such as Wholesale or Key accounts, and set the Currency. If it only runs for a period, fill in Valid from and Valid to. Turn on Default list if it should apply to every customer without a list of their own, then press Save.
Press the list to open it, then press Add price. Set the Item, Unit, From qty and Price, with an optional Discount %, then press Save prices.
For a quantity break, add the item twice: once from quantity 1, and once from quantity 100 at a lower price. The highest level the line quantity reaches is the one used.
For a long list use Paste a sheet: one row each with SKU, unit, minimum quantity and price, then Import rows.
3
Assign it to the customer
Open the customer in Customers & suppliers, press Edit, choose the list in the Price list field, then Save. The default list needs no assigning.
4
How the price is chosen
On quotes, sales orders and invoices the system looks in this order: the customer list, then the default list, then the Sale price on the item. A list that has expired or is switched off is not used. A price you type on the line yourself stays as it is.
Changing a list does not touch earlier invoices, but deleting it sends its customers back to the default list.