Dear Shopify Community,
I have a question: is there a chance to add a dropdown field to the sliding basket? I would like to provide customers with two options regarding delivery.
I’m using Dawn theme 15.0.1.
Thank you for your time and help.
Regards,
Adrian
Hi @adkowaty 
custom cart attributes are an advanced theme customization.
There is a guide for OLD vintage themes here: https://community.shopify.com/c/shopify-design/cart-use-cart-attributes-to-collect-more-information/td-p/613718
And that doesn’t not inherently allow connecting to actual shipping apis, cart attributes are mainly for textual information only that then in turn could be used in automations or apps as a separate step of a process.
If you need this customization then contact me for services
Contact info in forum signature.
ALWAYS please provide context, examples: store url, theme name, post url(s) , or any further detail in ALL correspondence.