chrome://flags/#enable-app-list-folder
Then click "Enable" next to "Enable the app list folder" and then click the "Relaunch now" button at the bottom of the page to restart the browser and enable the experimental feature.
"If enabled, user will be able to create app list folder by drag-and-drop," informs Google. It works just like in Android: drag one app on top of another to create a folder, then drag other apps to the folder.
Here's the Google folder from the screenshot above:
It's a simple feature that lets you organize your apps and reduce clutter. Unfortunately, it doesn't work well, at least not for me. After creating the folders, Chrome quickly removed them. Maybe it has something to do with syncing or maybe there are other bugs. It's an experimental feature, so I can't complain.
"These experimental features may change, break, or disappear at any time. We make absolutely no guarantees about what may happen if you turn one of these experiments on, and your browser may even spontaneously combust. (...) Please proceed with caution."
{ Thanks, Silviu. }