How can I show unchecked Save in address book at checkout when adding new shipping address?
Please suggest me.
I don't know which onestepcheckout you are using. But you can check in core checkout how it works refer below files
/vendor/magento/module-checkout/view/frontend/web/template/shipping-address/form.html
<!-- ko if: (isCustomerLoggedIn) -->
<div class="field choice" data-bind="visible: !isFormInline">
<input type="checkbox" class="checkbox" id="shipping-save-in-address-book" data-bind="checked: saveInAddressBook" />
<label class="label" for="shipping-save-in-address-book">
<span data-bind="i18n: 'Save in address book'"></span>
</label>
</div>
<!-- /ko -->
In above code the checkbox value is bind data-bind="checked: saveInAddressBook" />
This value is set in shipping.js file
vendor/magento/module-checkout/view/frontend/web/js/view/shipping.js
isNewAddressAdded: ko.observable(false),
saveInAddressBook: 1, //Change this value to 0
Redeploy your static content
clear cache and check