Also the tkdocs book is one of the books I reviewed, 3rd edition. The only mention of bindtags is a reference to the tkdocs website, which only documents the four default tags but not much else, which in turn references the Tk manual, which is hard to read as I don't understand Tcl.
I would recommend learning Tk and the details of how tkinter wraps Tk https://en.wikipedia.org/wiki/Tk_(software)
These resources might help:
https://www.tcl.tk/
https://tkdocs.com/
https://tkdocs.com/book.html