If you’re importing files, like PDFs, or images, you can just select them on your desktop and drag them into the Create Content Wizard that appears when you click the “New” button in Content Studio.
Thanks, it works just fine for one-off cases, but the scenario here is to bulk import significant number of custom content items mastered elsewhere (for example, car inventory or country list) and make them searchable.
Create a script that uses the content API to import
Import using the node level format.
To understand how the import format looks, create some dummy content for your content type and use the export function in toolbox. Now, make your data available in this exact format and run the toolbox import on it!