Well, if that title isn't confusing, I'm not doing my job right.
Today's post starts a three-part mini-series within the Notebook series on building customized tabs in a DrawingArea. There's a ton of stuff to go over; that's why it's in three parts.
Anyway, the fun begins right here: https://gtkdcoding.com/2019/10/15/0079-notebook-iii-custom-tabs-i.html