Lets talk European keyboards, [ is alt+8. This has been a long running frustration for apps that don't allow remapping but use the US/UK keyboard as standard.
Control + ] or Control + [ is frequently the escape character, although not always. You can usually type it with Control + some key right of P. In the Swedish keyboard, use Control + å, German is Control + ü. But it does vary wildly, French is Control + 6, Hungarian is Control + 5, and so on.
I'm not sure what "European keyboard" you have but mine doesn't work that way. [ is a key on my keyboard I don't need to press any modifiers for.
It's also a bit odd to generalise this to European keyboards as some layouts vary wildly on the continent based on the lack of or added letters to their alphabet. Also, UK is in Europe so would count as a European layout.
