This was bugging me SO much.
The problem
If you had to use the autoStep because you had no workarounds left and really wanted the start/stop behaviour, for multiple lights it would look like this:
Same for the stop, three autoStep 0 .
Apparently there’s nothing wrong, but that launches three timers that may not be in sync so the steps will generate popcorn-effect 99% of the time and, worse, the timers may not stop at the same time and a light could end up with an extra step, especially if the interval is short.
The effective but visually ugly workaround
Version 2025-11-17 adds a little trick:
autoStep 10also DEVICE_ID
Now a single autoStep can control additional lights as long as they use this driver, specifying the device ID you can find in the advanced website (AWA). You can add more than one device, comma separated with no spaces (sorry I don’t want to mess with the parser now…)
autoStep 10 also DEVICE_ID1,DEVICE_ID2,...
The advantages are clear: only one timer so no sync issues or risk of not stopping at once and the commands to step are sent virtually at the same time. While that doesn’t guarantee no popcorn-effect, the difference is noticeable and most of the time the steps are perfectly in sync.
Now it would look like this:
Which is not that ugly after all and if you want to change the options like interval time or transition time you only have to change it in one place, not in three. 
Now there’s no advantage on using buttons with auto-repeat or the virtual scene switcher other than not having to deal with device IDs or text inputs. In fact, now autoStep is the best workaround for emulated dimming (at least technically).
Update Nov 24th 2025: Since device IDs are too long for the text input of the app, now you can write the IDs in a short form so they fit.