Solution
Sample code shows adding address values to a customer record
let cusRecord = record.create({
                            type: 'customer',
                            isDynamic: true
                        });
cusRecord.selectLine({
                            sublistId: 'addressbook',
                            line: 0
                        });
                        var addressBook = cusRecord.getCurrentSublistSubrecord({
                            sublistId: 'addressbook',
                            fieldId: 'addressbookaddress'
                        });
                        addressBook.setValue({
                            fieldId: 'country',
                            value: cusAddress.country_code,
                        })
                        addressBook.setValue({
                            fieldId: 'addressee',
                            value: cusData[i].company,
                        })
                        addressBook.setValue({
                            fieldId: 'addr1',
                            value: cusAddress.address1,
                        })
                        addressBook.setValue({
                            fieldId: 'addr2',
                            value: cusAddress.address2,
                        })
                        addressBook.setValue({
                            fieldId: 'phone',
                            value: cusAddress.phone,
                        })
                        addressBook.setValue({
                            fieldId: 'state',
                            value: cusAddress.state_or_province,
                        })
                        addressBook.setValue({
                            fieldId: 'zip',
                            value: cusAddress.postal_code,
                        })
                        cusRecord.commitLine({
                            sublistId: 'addressbook',
                        });