I have looked in the input configuration menu and in InputTemplates.txt inside the game folder and have not found such a key. Hitting escape, clicking on map and finally on full map is rather tedious.

Thank you. That's what I was worried about. I've switched to using esc-enter-enter, that's a little less annoying than using the mouse, but still bad.

I don't know why anybody would not implement such an important feature.

It's because it is a console port. With a gamepad, it is a relatively un-annoying two button press (similar to the esc-enter-enter you are already using).