We have just launched a new backend for bulk uploads in Google Ads Scripts. Starting today, you can opt into the new experience by specifying the useLegacyUploads flag when creating a new bulk upload:

var upload = AdsApp.bulkUploads().newCsvUpload(columns,
    {useLegacyUploads: false});

For now, if you don't specify a value, the default will be true, which will result in no change of behavior from before this feature. Starting on July 12, 2021 we will change the default to false, but you can still opt out for a time by explicitly passing useLegacyUploads as true. On February 1, 2022, we will disable the use of legacy uploads altogether.

We have tried to make the changes here as backwards-compatible as possible, so in most cases your existing uploads should continue to work fine even on the new backend. However, creating video ads which specify a media ID will cease working on the legacy uploads on or after July 12, when we change the default, so if those are important fields to you, make sure you do not manually override to use legacy uploads.

The new backend is exactly compatible with UI-based bulk uploads, which is an improvement over the existing bulk upload system where many columns have different names. This should make it significantly easier to set up bulk uploads by basing the format from the UI. Additionally, a few new features are available, including label manipulation and updating manager accounts.

If you have any questions, please leave a post on our forum so that we can help.
- Mike Cloonan, Google Ads Scripts Team