Answer
The event for clicking the middle mouse button three times is "Triple-Button-2".
Work Step by Step
Here's an example of how you can bind an event to a canvas when the middle mouse button is clicked three times:
from tkinter import *
def processTripleClick(event):
$\hspace{4mm}$print("Triple-Button-2 event detected")
root = Tk()
canvas = Canvas(root, width=200, height=200)
canvas.pack()
canvas.bind("", processTripleClick)
root.mainloop()
In this example, when the middle mouse button is clicked three times on the canvas, the function processTripleClick will be called and the message "Triple-Button-2 event detected" will be printed to the console.
