Broad categories of customers
Think about customer groups as broad categories of customers you work with. These could be retailers, wholesalers and end-users for instance. There's usually a notion of price adjustment associated with customer groups, and if that's the case your web store will reflect automatically these prices adjustments in your online catalogue. You can find these settings on Customers groups tab in STORE / Merchandising section.
Create as many group names as necessary and associate a price modifier/discount either in % or in the currency of your system.
Assign individual leads to customer groups from your lead grid, or lead details screen
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You can also assign existing clients to the appropriate customers groups from your Clients tab on Dashboard (STORE / Go to Dashboard).