How do I search for a specific drawing or folder?

This currently depends on the platform you are on:

On Android, Concepts now includes a Search button in the Gallery. Tap on that, then type the name of the drawing, the folder, or anything you've entered into the folder notes field. As of May 2024, you'll also have the ability to search for handwritten notes inside drawings, if you're a subscriber.
On iOS, Concepts does not yet have a built in search feature, but you can search for drawings using Spotlight (iOS' built-in search) or the Files app. Swipe down from the top-center of your device home screen to reveal the search option.
On Windows, Concepts does not yet have a built in search feature, but you can search for drawings and folders in Windows Explorer and open them directly from there.