Hi @boxter,
Welcome to the Cayenne Community, glad to have you.
We do have an updated features planned on our roadmap to increase the power of triggers, like conditional triggers that will fire based on the state of other dashboard items, time activated triggers, and even triggers containing your custom code, which will really open up this feature for more powerful solutions.
It might be a little hacky but you could accomplish the first request (Allow switch on dashboard to enable certain triggers) now by making a light switch button widget on your dashboard and setting the trigger to fire based on the state of that button. It doesn’t even need to be connected to anything on an actual Pi. Definitely not ideal but to tide you over while we improve the Triggers functionality.