OK....found a solution. I added the --listen option. Setup a pipe that I could read/write on. Fired up yad to get its input off this pipe.
Then I fed the data to populate the list into the pipe. I created a button to select all with a command script that gets invoked when
clicked. in this script, it selectively will initialize the contents of the list and re-populate it depending on whether I want to toggle
the values ON / OFF. Much faster than reloading the whole display.