I just upgraded from Pro 12, so I don’t know when this behavior was introduced but I need to turn it off: whenever I change a plug-in parameter or mute a channel, an automation Lane opens up for that channel or group. I really can’t imagine how this “feature” would help anybody. I tried to address it using the automation panel - checked the used only box, but it doesn’t change anything unless I hide all first.
This is a new feature in Cubase 15. You can disable it in the settings in the automation field. It’s called Last Touched Parameter.