Possible error on help page about variables in a design

Issue in ./help/main/c-recommendations/c-design-overview/customizing-a-template.md

The fourth paragraph down states: Any variable sent to Recommendations in the productPage mbox or the CSV upload can be displayed in a design.

I don't believe this is accurate. Only single-value variables can be used to display in a design. Category (multi-value) and other custom multi-value attributes aren't displayable in a design last I tested.

Open help/main/c-recommendations/c-design-overview/customizing-a-template.md and review the fourth paragraph. Verify the stated displayability of single-value, category, and other custom multi-value variables, then update the wording so it accurately reflects which variables can be displayed in a design.

Written by the indexing model from the issue text.