Hi all, I wonder, if there is a way to turn of the light in the printing room of the printer. Or do I need to do it always via the user-panel at the printer? A button in octoprint will be great.
Try M355 in the terminal. (https://reprap.org/wiki/G-code#M355:_Turn_case_lights_on.2Foff)
If that works you can insert a button in the control panel with the Custom Control Editor or Editor Collection
M355 S0 or M355 S1 isn't working. 
Anycubic just replied, that the light cannot be turned off via gcode.
So... add an inline relay...?
As I am using a home automation, I wonder, if it is possible, to place a button in Octoprint and if I push this button, a dedicated url will be requested (triggering some actions.
Is there a way to add Url requests which will be triggered automatically if an event occurs (like print jibe done)?
Search the forum here for Gcode System Commands. A command like OCTO901 might correspond to turning something ON and OCTO900 would be the one for turning it OFF again. You'd then add a custom Control button on the Control tab to run one of those.