Kind of a simple question, I just don't want to get caught by surprise.
Say I'm down to 6 energy and I want to use an elevator. Will the game automatically pull 4 energy from CE if available, or do I get some sort of confirmation? I don't want to dip into CE reserves without any warning.
It gets used automatically. Also, Mist Energy is always used before Crystal Energy.
So, in your example, assuming you have 20ce and 6me, using a lift would leave you with 16ce and 0me.