Magento – Place order button in Magento 2 checkout

Solved the above issue. If you want to avoid the update and cancel button under the billing address and implement the update functionality when click on place order button, no need to go through the above way.

File path: _vendor/magento/module-checkout/view/frontend/web/js/view/payment/default.js

First copy this file and place in your theme folder. Then, just replace this below code with the placeOrder function and hide the update and cancel button using css- display:none;

        placeOrder: function (data, event)
        {
            if($('.billing-address-form:visible').length == 0)
            {
                $('.action-update').click();
                var self = this;
                if (event) {
                    event.preventDefault();
                }
                if (this.validate() && additionalValidators.validate()) {
                    this.isPlaceOrderActionAllowed(false);

                    this.getPlaceOrderDeferredObject()
                        .fail(
                            function () {
                                self.isPlaceOrderActionAllowed(true);
                            }
                        ).done(
                            function () {
                                self.afterPlaceOrder();

                                if (self.redirectAfterPlaceOrder) {
                                    redirectOnSuccessAction.execute();
                                }
                            }
                        );

                    return true;
                }

                return false;
            }
            else
            {
                var firstname = $("input[name=firstname]").val();
                var lastname = $("input[name=lastname]").val();
                var street = $("input[name='street[0]']").val();
                var city = $("input[name=city]").val();
                var regionid = $("input[name=region_id]").val();
                var postcode = $("input[name=postcode]").val();
                var countryid = $("input[name=country_id]").val();
                var telephone = $("input[name=telephone]").val();

                if((firstname == '') || (lastname == '') || (street = '') || (city == '') || (regionid = '') || (postcode = '') || (countryid == '') || (telephone = ''))
                {
                    $('.action-update').click();
                }
            }

        },

I'm not sure I understand the question fully, do you mean you want to call a KO HTML template from another template/module?

If so the I believe the following markup works (unable to test currently):

<!-- ko template: "Package_Namespace/template-name" --><!-- /ko -->

Or alternatively you can define the template in an object and pass a property like so:

<!-- ko template: propertyExample --><!-- /ko -->