Paste a parcel locker ID from a map in the cart as a variable into the checkout shipping method list

[VortexVR]

Dear Shopify,

I have a Custom App that connect to one of my courier firms and selects the 3 closest parcel lockers and presents them inside the Checkout Shipping selection page. I have attached a screenshot for this.

Now, I would like to add a widget-map into my cart page (as I dont have access to my checkout.liquid file, as I am on a "Shopify" plan). This widget will fetch the parcel locker or parcel point that the customer selects from, and I would like to pass this selection to the checkout and the checkout shipping selection page.

Would this be possible to show the selected parcel locker from the widget map as a variable that is later shown inside the checkout shipping option as a preselection on the first row?

Since our custom app can fetch parcel lockers from an api and show them inside the checkout shipping list, why would this not be possible?

The widget documention:

https://widget-maps.paxy.pl/docs/intro

I have the widget code if needed!

Sincerely,
HUGE Thanks to you all!