The app builder should use Data Loader to quickly insert a list of over 60,000 net new Accounts. Data Loader is a tool that allows users to insert, update, delete, or export large amounts of data from Salesforce using CSV files or database connections. Data Loader can handle up to 5 million records at a time and supports features such as bulk API, batch operations, mapping files, etc. Data Loader is ideal for loading large data sets into Salesforce quickly and efficiently. Lightning Object Creator is not a valid tool, as it cannot insert data into existing objects. Lightning Object Creator is a tool that allows users to create custom objects from spreadsheet data by uploading a file and mapping columns to fields. It cannot load data into existing objects or handle more than 500 records at a time. Import Wizard is not a valid tool, as it cannot handle more than 50,000 records at a time. Import Wizard is a tool that allows users to insert, update, or delete data from Salesforce using CSV files or Excel files. Import Wizard supports standard objects and some custom objects and provides features such as field mapping, duplicate detection, data validation, etc. Import Wizard is ideal for loading small data sets into Salesforce with more control and accuracy.