在“工具”面板中，点击“渐变”工具。 点击要编辑的渐变。 通过点击渐变下面的滑块来更改颜色。 通过点击渐变示例上方的滑块来改变不透明度。 调整中间的菱形来设置中点。 调整渐变的“平滑度”，以获得彩虹效果的颜色。 保存你喜欢的渐变，供稍后使用，或者免费在线获得更多渐变。

I'm interested in that, but I only have a few mins. Can you give me at most the first 500 characters of a detailed explanation in English about that?
You can set presets. You can create precise color arrangements. You can even edit preexisting gradients to perfect them. To view the Gradient Editor, select the gradient tool like normal. Then click the example gradient that appears in the bar at the top of your screen. You should see:  A variety of preset gradients An example gradient with adjustable sliders. Opacity and layering information. Options to make a new gradient, load old ones, or save a creation. You can also manage the presets, or