How to type a backtick (accent grave or “`”) on a European (Dutch) keyboard

Some keyboard layouts (like Finnish, but not Danish) have a normal backtick under ⌥⇧´, so for example ⌃⌥⇧´ opens the console in Sublime Text.

If you don't want to switch to another keyboard layout, you can use Ukelele to modify the Danish layout. See this question.

On the US keyboard it is in the top left corner to the left of the 1.

You'll see it just under the tilde sign (~) in the top left of the keyboard.