How do you save an entire folder from Google Chrome's Developer Tools' Sources tab?

It's not possible to do directly with Chrome, so I made a batching extension to automatically fetch resources to the Downloads folder. You can have a try.

Save All Resources Extension | Github

Currently not possible.

"Saving whole folders is not currently supported."

https://github.com/GoogleChrome/devtools-docs/issues/30#issuecomment-76999063

Here is the corresponding issue in the Chromium Bug Tracker: https://bugs.chromium.org/p/chromium/issues/detail?id=675894

Just do right click -> save as html -> in type select (complete webpage).

Works on OSX.