Thank you for reaching out to us today! In fact, you can add emojis to the subject line of an email. When editing the subject line for a 3ge campaign, there should be a little smiley face on the right side of the text area. If you click that you can add the emojis you need to bring some extra flair to your email.
For additional details, you can refer to this article regarding subject line emojis.
Feel free to reply to this thread if you have any additional questions or comments.