I had about 7000 transactions to delete and came up with this solution. This is for linux but I'm sure there are similar options on Windows and Mac. 

I installed xdotool that lets you script mouse moves and button clicks. I then worked out the screen coordinates for the 3 clicks needed to delete a record and set a 1 second delay between clicks. I could then run the script, leave the machine and 5 hours later I was done.

This is the script that worked for me when QBO fullscreen in chrome:

#!/bin/bash

for i in {1..7000}
do
       xdotool mousemove 599 599 click 1
       sleep 1
       xdotool mousemove 2200 650 click 1
       sleep 1
       xdotool mousemove 1500 820 click 1
       sleep 1
done