Indeed, we can use the GroupHeaderTemplateDirective
in order to place any HTML and/or text in the group headers.
Unfortunately, currently there is no other built in functionality that could help us to achieve the desired behavior.
If you have the time, please log a new feature request in our UserVoice
portal, which helps us to get ideas about any new features and enhancements of Kendo Ui for Angular. Thank you in advance.