Here it is: https://gtkdcoding.com/2019/10/11/0078-notebook-ii-multiple-tabs.html
Blog Post #78: Notebook, Part II
Ron Tarrant via Digitalmars-d-learn Fri, 11 Oct 2019 07:20:42 -0700
Continuing the series on the GTK Notebook, we look at multiple
tabs, reordering tabs, and stuffing images into tabs. Exciting
stuff, no?