Hi,
We are looking at converting our existing POS system to Shopify, but before we take that leap, I need to figure out a use case and the documentation is not helpful.
We would be utilizing Local Delivery to setup delivery charges, but we need to have the ability to set a delivery date somewhere in the checkout process. Based on what I am seeing, there doesn’t seem to be a way to do it natively or within an app (at least not without going to Shopify+, which is prohibitively expensive for our needs).
I can’t be the first one to have this requirement, so I am reaching out to see if someone has figured this out.
Thanks!
Hi @kevinnanson 
Native alternative for additional info for orders on POS can be just using the order notes, or using metafields on the customer, or tags.
Yet everyone can have different needs.
You just have to shortlist from the app store
https://apps.shopify.com/search?q=POS+local+pickup+date&features[]=point-of-sale&categories[]=orders-and-shipping
Or in some cases use the api to build a custom app to suit specific needs.
Ok, so here is where I am stuck. I am a developer by trade, so creating an app for us is something I can do, but I am not sure where I should be setting that up. Based on my understanding, putting these details on the checkout page is the most logical place, but the documentation states that I cannot change the UI there. So my question is, where do other businesses (or apps) put these details?
For development , see the .dev docs and dev community
https://shopify.dev & https://community.shopify.dev
Doing dev or not , know POS is not the same as cart, cart is not the same as checkout
So adding stuff for POS to have order information is not always the same as customizing checkout.
You either need to just dive into the dev docs, and just test a series of apps so you know what’s possible, like by also to trawling through the apps feature tags lists , like scheduling
Abandon all logic ye who enter here /s, such logic only holds if you control the entire stack( and compliance responsibility).
Shopify Plus plans can use checkout extensions.
Everyone else it’s mostly getting that info before checkout in product page, in the cart, or after post purchase.
As stints , for the online-sales channel THEME, just use line-item-properties on the product, or cart-attributes that carry through checkout.
Or a stint can be to add a literal “product” to the cart that represents the date(or other info; 
but utility of this varies depending how downstream systems consume such info.
These methods are assuming the customer will even select local delivery in checkout, if they don’t choose local delivery the info you made them give is moot or possibly means cart-validations(shopify-functions) is required to enforce things.
Yes it’s a mess becaues it’s a big platform now, no it’s not likely for shopify to open up checkout to any and all arbitrary changes for all plans.
So be sure to have the merchant/owner submit an actual feature request to a shopify support-advisor such as through the help docs chat