It’s easy enough to set up window sets to stop that clicking. There are also strategies for setting up your windows to stop that from happening. If you are spending %25 of your mouse clicks on windows then you need to RTFM on how Cubase does Windows management. It’s not great, but it can be worked with. My guess is you want it to work like newer interfaces with tabs and docks. But, it doesn’t. It’s that simple. It is an old school child window system. And, it was arguably never a properly implemented one at that.
But, as I’ve said, you can learn to use it as intended and it won’t take that many clicks and you can cut down on the frustration significantly.
As mashedmitten said, this has been a LONG time bitch point for users.