If a font is added to QDS we do not reset the puppet. Therefore, the font is not loaded, and the puppet has to be refreshed to preview the new font properly.

Refresh puppet:

void FormEditorView::resetNodeInstanceView()
{
    resetPuppet();
}

If resources go through the item asset library this function is called:

void AssetsLibraryWidget::addResources(const QStringList &files, bool showDialog)

There is also the resource handler. Adding any resource will always go through the handler registered for .ttf files.

void DesignerActionManager::createDefaultAddResourceHandler()

Currently only the asset library does add new fonts/assets using ::addResources.