Hi All,
I have created a switch toggler to switch my HUE lights on/off.
Now I want to go to step 2…
I want to enable a specific Hue scene when pushing a button (or something).
I already have a rule which set a scene when the state of a light changes from off to on.
But now I need a trigger based on an input from a user from the GUI…
Is that possible, and if so… How?
Of course. Create a Switch Item and use that in your UI and to trigger the rule like any other Switch Item. Or you can have a widget call a rule directly (assuming MainUI).
Sorry, extreme beginner here 
When adding a rule, I have 4 options for triggers (item event, thing event, time event, system event).
None of these seem (to me) to do what I want to accomplish.
To trigger a rule from a Switch Item you will trigger it from an Item Event.
If you have the UI Widget call the rule directly as an action, there is no rule trigger required.