Build rules → Generate widget file → Upload to Shopify (no Admin access needed)
cs-col-[handle] e.g. cs-col-shoesNo rules yet — add one above!
In Themes → Edit Code, find cart.liquid or sections/main-cart-items.liquid. Paste this line above the cart table (outside the <table> tag):
Go to Snippets → Add new snippet, name it cross-sell-widget. Then use this admin page to generate and upload the file content.
Add/remove rules here → click Generate Widget File → download → open cross-sell-widget snippet in Shopify → select all (Ctrl+A) → paste → Save.