layers
I think a layer feature would be incredibly useful for learning. With layers, I could organize content much more effectively: for example, I could draw or write something on one layer and place the explanation on a separate layer underneath.
From a learning perspective, this would be especially helpful because I could first work with the top layer on my own and then reveal the lower layer afterward to check the explanation or solution. That would make the learning process much more interactive and structured.
I have seen a similar function in Free Note, where you can use different layers and show or hide them with an eye icon. I think that is a really powerful feature, and it would be fantastic if Goodnotes offered something similar.