You can also discover what is slow, by adding timeline notifications, or log cards (Simple Log app f.i.)
-Notification is sent at the time the lights turn on → the trigger is delayed
-Notification is sent at the time the switch is turned on → the lights respond delayed
Also, Homey is not good at sending too many signals at once.
And, it fires all action cards at random (asynchronized)
It’s best to add a little delay between every 2 or 3 lights.
However, the flow editor’s smallest settable delay is one second, which is quite absurd.
When you group your lights, using an advanced virtual device (Device Capabilities app) or < group > app, devices are commanded synchronised (one after another, not at once), and with the < group > app you can add a delay in the milliseconds range if you like, it is added between every light command
