I have the same question. I keep adding gradients but they don't show what they are in the left hand gradient map They just keep piling up one on top of another. Is there a good tutorial which explains this new feature for us soーcalled "newbies".
PS. I'm working through a "new features" tutorial on gradients and having a few problems. This is what the guy shows on his machine 1 and what I have on mine. 2. Something no quite right.
Adobe made using gradient presets much more difficult by putting all the gradients presets that before you had to append in captions that now show you when you click on gradient map. Once you click on a gradient you have to click on the gradient to get to the gradient picker. It is cumbersome to use compared to the legacy gradients and takes up more space. JKost has a video on the new gradient presets that is somewhat helpful but if you are a newbi you will have to spend time learning the changes adobe made. the prior legacy method was much easier to use. I spent over an hour chatting with an adobe support person before I was able to fully understand the new process. I suggest you do the same.