You can use Item Plan to generate Spreads (such as Size Spread or Channel Spread) that you can then use in Assortment Planning while quantifying your size level buys.
1 - On Item Plan go to the
Toolio - Size Scale view. This view allows you to filter your sales for the trailing 4 weeks for a particular style and groups the data by Size.
2- Select the sizes that you want to include in the Spread
Right Click > Generate Spread > Size
4 - Give a name for the the Size Spread and hit
5 - Within Assortment Planning, while you're inputting your Size Spreads (or Size Scales), you will be able to select the Spread that you've created.