Well - don't feel like an idiot. I've just had to Google how to exit a turret in Battlefront II as well.
It does beggar belief how the game actively tells you to hold down the E key to 'enter' a turret and yet you don't hold down the same key to exit it? I know - let's just give that to the G key instead.
Similarly with the cards option - why do I have to set aside four valuable keys to select each one? Why couldn't I scroll a mousewheel in one direction, just like I can with the weapons? Works absolutely flawlessly in over 1,500+ hours of Warframe where mousewheel down rotates my gear and mousewheel up cycles the powers. It's exactly that kind of rapid choice that you need when things get busy on screen - rather than thinking did I set Card 1 to Q, Card 2 to F, Card 3 to X before realising that you've thrown a grenade in a closed environment.
There appears to be a general dislike for the players on Keyboard & Mouse controls in the last decade - almost like developers want to go out of their ways to hinder us. Some companies 'get it' - ironically, it tends to be a lot of the smaller games companies that allow a much more free reign on the player's controls. However, nothing but nothing pushes my buttons (excuse the pun) more than when you have to set aside a key for the most abstract of game controls that you might only ever use once. "Not all controls have been assigned - please retry" ARRRRGGGGHH!!! :P