Is there one? Please implement one otherwise, for example ctrl + q/w/e/r
+1 was going to make a thread on this, but found yours .
In an intense fight levelling up (on purpose or not) could swing a fight in your favour not only with the extra hp/mana, but the ability to get another skill.
Especially early game, when going for/running from a first blood gank many times in dota that level up to level 2 would save me from an otherwise grim situation (quickly hit O+skill hotkey).
My friend tried to do that when we were chasing down an enemy and he lost track of him in the time it took for him to move his mouse to click the skill, then back to the hero.
It's not a big deal to have to click it, in most situations, but it would make it simpler/easier if a hotkey was available as well.
"Victorious warriors win first and then go to war, while defeated warriors go to war first and then seek to win."