Enable the Developer Menu The option to add a drop-down list is located in ...

To insert a drop-down box, you'll first have to unlock Word's Developer Tools. Microsoft Word 2010 and later, including Office 365 and Word 2019, come with Developer Tools, but they aren't visible ...

The best practice is to create a separate worksheet for your drop-down list. To create a new tab, click the "+" icon next to the last tab in your spreadsheet. Double click the tab to rename it.