Re Macro That Runs Until Key Is Pressed
Hey Simon,
The only web browser I know of that supports TIFF files is Safari, and the ones you posted in the topic above were not displayed by Safari on macOS 10.14.6 Mojave on my system.
Henceforth please do not use TIFFs for illustrative purposes on the forum.
I have converted the current crop to JPEGs for you this time. 
Take Care,
Chris
(Keyboard Maestro Moderator)