Download and install 7+ Taskbar Tweaker. It has an installable version, and a portable version. Choose whichever one it is you want to use, and run it. The app offers a whole host of different things you can tweak. To disable show desktop, enable the ‘Hide the Show desktop’ button option in the Other section at the bottom right.
Close the app after the option has been enabled and the Show desktop button will be hidden. You will no longer accidentally click on it and minimize everything.
If you want to keep the Show desktop button but disable the ‘peak’ feature, you can. Peak is where, when you hover the mouse cursor over the show desktop button, it shows you your desktop. When you move the cursor away, your windows return to their original views.
If you choose to disable Show desktop, you can still minimize everything on your screen and go to your desktop with the Win+D keyboard shortcut. Show desktop is a feature that has been a part of Windows since before Windows 7 and it was far more useful there with the Aero theme that Windows 7 had. With Windows 10, users may not like it as much and might prefer the keyboard shortcut over it. You can also mimic Show desktop via a four finger swipe down touchpad gesture on Windows 10.