@littleviolette Hi, it can’t be run in the Admin UI here.
Using the Theme CLI, you can easily create a theme component on your computer.
Then, you edit the file with a text editor of your choice (like vscode) and add the code in the initializer. You make a file in /javascripts/discourse/api-initializers/my-header-icon.gjs and you paste the code in it. You can also change the default values in about.json.
The next step to install the component on your production forum:
- you can either put the component on Github and in the Admin UI, use the repository link to install;
- or you zip the directory on your computer, and in the Admin UI, you install it from the device.
Give it a shot and let me know if you have any issues!