Or, if we are really thinking outside the box…
You could get a smart outlet that is compatible with IFTTT without using a hub. Then you could plug your ST hub into the outlet, and let IFTTT turn the power on or off. With no power to the hub, all pistons stop immediately.
The global variable that @Gopack2 suggested can work, but it requires a bunch of extra code, since things will often continue to run for awhile after the variable changes.
IE: Walk past motion sensor… 1 minute later it goes inactive… Then you flip the switch to pause the pistons… Shortly thereafter, the motion detector has been inactive for 5 minutes, so the code continues.
Again, it is possible, but all of the code needs to be thought of quite differently if you go that route.
Please don’t take this wrong @GGexe, but the only reason I ever pause a piston is when my code is in the development phase. A well coded piston would never need to be paused.