I realise I can use the thermostat scheduler, but this one is a simplified version with only time and presence variables. eg, other rooms will have door sensors and motion triggers.
Can I use the changing state of a variable as trigger to an action in Webcore?
regular variables are not a trigger (a global variable can be a trigger).
You could do the 'changes' yourself by having another variable that is the initial value, then you can compare if they changed. (and at the end update the variables to be the same).
There are folks really good at optimizing pistons in the webcore forum: