If you have your options / sizes set as Product Varations you can set display options to allow adding multple variants by at once.
Add multiple options at once - how to set for all Products with variants via global setting.
- Click the blue E-COMMERCE button then DISPLAY OPTIONS.
- In the View Product Page Options section, click the checkbox Display variants with multiple option/quantity form in the sidebar
- This will show the options with a quantity field next to each one. (Multiple Qty List of Variants format)
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Add multiple options at once - change the display option for a single Product
- Edit the product and click the OPTIONS/SIZES tab.
- Change the DISPLAY FORMAT to one of the following options
- Multiple Quantity List of Variants
- Multiple Quantity Table of Variants
- Multiple Quantity Table of Variant Sizing
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A product variant containing sizing and sku code set to Multiple Quantity Table of Variant Sizing