Now you can set customer groups by default when creating new customers from sell.
Step 1. Go To Setup Menu
Step 2. Click More Menu then Click Module
Step 3. Click Tab Contact and Select the Contact Group
For example, I Choose "Silver"
II. Add Customer From Sell Menu
Step 1. Go To Sell Menu and Click Button "+"
Step 2. Fill Customer Form then Click OK
III. Check the Customer That Has Been Made
Step 1. Go To Contact Menu and Click the Customer Name
The newly created customer will immediately enter the silver group