Shared Drafts for Shared Mailbox
This feature lets you share Gmail drafts with your team-mates who are using the same Shared Mailbox.
To use this, click on the button shown below while composing an email/ replying to an email
You’ll be able to save this as a Shared Draft in the dialog box that opens. The draft is automatically shared with users of the Shared Mailbox. If you want you can also send a notification to one or multiple users about it.