I use GN for my work of building design.
Layering would be greatly useful to sketch multiple version of a design.

Layers. I past shapes into my notes and write on top of them. It is hard to work with text on top of graphics. For example, entering risk on top of this risk graphic.

exactly what I have been missing

I also miss layers - perhaps having a look at lecturenotes on an android-device could be inspiring in this regard...

I use GoodNotes to draw a lot of flow charts and most of the time that I need a tool that can switch between layer so that I can erase or edit just a portion of arrow in the same page. Most obvious example is like layers in photoshop or Sketch apps.

Allow Goodnotes to run in the background and select an option to annoate any screen.

Or from Goodnotes app, import a transparent layer that includes iPad running other apps as the Goodnotes content.

Annotations would not be "part of" the running app - just placed over them (could save as "export current screen with notes as PDF or Goodnotes file."

BRING SOMETHING FORWARDS / BACKWARDS!
I just wasted 2 hours of work because I ve done this lovely graph with notes, drawing and images and then I needed to place an image on top. Result? I can't bring the image backwards... all the work is LOST!

In school I want to substitute the blackboard by GoodNotes with a projector. I like to make some notes that the students doesn't the on the projector screen. Multiple layers (with option shown on projection or not) would be nice.

I agree, layers would be a useful addition.

Please add this feature.
Thanks.

Layers would help me. I want to write consultation notes and sometimes need to print them. If I could just print the "new layer" on the previous printed paper copy I wouldn't have to print out the whole page with each new addition, just feed the old one into the printer and print the new layer as an addition.

This feature would allow more precise edited without messing up previous work. If file size is a issue add a flatten layers feature.
Cool app by the way

I would be really happy with the possibility to use layers. For example Zoomnotes has already offer it...

Layers would make the app more useful

I use goodnotes exclusively when I am designing buildings and putting objects on layers would be such a useful feature

I use goodnotes for sketching and layers would enhance the product a great deal

Add a lock text/drawing feature so that you can selectively not erase it (i.e. Lock it, write over it and be able to erase only what you wrote over it.)

I am a teacher and give live presentations multiple times, and reuse year after year. Transparencies would be amazingly great. Now I have to go back with my eraser and carefully erase changes to each page between class periods. Not simple, fast or efficient.

I use this app for my sketching my architectural designs and the ability to work in layers would be so helpful. Rotating hand drawn notes/sketches would also very nice. If these features are too specialize for most people Goodnotes may want to consider selling these features as an optional add-on. This is by far my favorite app.

Yes and the ability to order them like "send to back" and "bring on top"