I just tried it with one of my apps where I use a form button to create a new record. That triggers the onchange and runs the script to copy the value to another sheet, so as far as I can tell, it should work. An alternative would maybe be to split your switches into seperate sheets, set up relations to those sheets and create an inline list that links to each sheet. Then when you open up the list item, you can click on the pencil to edit the switch. That will allow you to use the Date/Time special value to automatically fill in the date related to that switch. It’s a really ugly solution and your use of dates instead of switches is probably a better solution in this case. With your scenario, I would press on with trying to get the script to work with the trigger.