My workplace started using Gitbook as a way to create documentation for his own software. My boss paid for the PRO option, and now tries to customize our page documentation. We saw that we could use our own icon in our Space header, but couldn't reproduce it for the page header shown in the content table. Instead, we can only add an Emoji to decorate the page, and it seems impossible to change it at first. Is there a way to do so with code or any other method?
A screen of the said area

Thanks!
- I Searched a lot on Google, without success. Some methods relate about changing the API linking gitbook to github's emojis, by using a script like tempermonkey/greasemonkey. But I suppose it's only effective for the user having the said script installed. I'd like to change it for every user without the need of installing external scripts.
You're able to change the emoji, or remove it by clicking on the emoji itself in the editor.
See here:
emoji picker
That being said, you unfortunately are not able to change the emoji to an image