Not possible to add.
It would be great to be able to use any mat-icon. For now, I would love to at least get a complete list of the icons available. I’ve noticed that the list changes depending on the context of what the icon is for, although you can change the icon name in the viewConfigDiff to any available and it works (as long as you know the available icon names)
Unfortunately, there is currently no way to add a new icon in the icon list for Freedom UI.
However, a task has already been registered in our R&D team to consider and implement such a feature in future releases. In case you would like to check what stage this task is at, I am sending you the task number: PR-28339. Feel free to share this number with us at any time and ask your questions.