Help, Please!

What you can also do is copy and paste the banner onto a Google Docs sheet paper thing. Then, copy and paste it into your summary from the Google Doc. That's what I do. It's the same process for adding a banner into a chapter. Credit to @WaitingForMyHogwartsLetter for telling me this.
That's what I find easiest to do, and it usually works. I do usually have to try a few times though. Hope you manage to get it!