Hi Pavel,
In Woocommerce I have a variable product (item XYZ and 500 units in inventory). It uses an attribute "Pack Qty" to display dropdown variants for pack sizes. So customer can only buy item XYZ in packs of 10, 50, or 100. Each pack has a SKU: XYZ-10, XYZ-50, XYX-100. Product is set up with limitation, sold in quantities of 1, so that customer cannot order multiples of any pack.
I don't want to allocate the stock of XYZ to each pack size in advance. So I need to track stock at the parent item level. Any time someone orders an XYZ pack the stock needs to be reduced by the quantity the variant SKU represents.
Is that more clear?