To edit custom attributes for multiple accounts at once, click the Bulk Edit link at the bottom left of the custom attributes screen.
After you click this link, you can copy custom attributes from one account to other accounts.
Tip: If you have several accounts with similar custom attributes, we suggest filling out the attributes for one account, saving them, and then copying them to the others.
In the video below, we show how to copy custom attributes from the 'Acme Corp.' account to three other accounts: