Thank you so much for using Amplify Shader Editor!
I've read your posts and it seems that you want a gradient to be dependent on the fragment Y position, but then your are multiplying the saturated Lerp result with the World Normal x component and I'm not quite sure why.
I do apologize for this but Is it possible for you to give further information on how the gradient is suppose to behave so I can better help you out?
No problem at all, I hope I can help you out. And thank you for the cool drawing It's quite the interesting challenge. Let me give me some thought and I'll let you know as soon as I figure out something that might help.
Like you previously said, your solution may come from using a triplanar technique and our Triplanar node would probably do the trick.
After creating the this node you would go to its node properties and set the Mapping option to Spherical. Your gradients would be saved into textures and then set as the Top, Middle and Bottom textures of the Triplanar node. After that you'll need to play around with the falloff value as it controls the interpolated blend between the projected planes.
Having a big falloff value ( p.e. 100 ) may be what you need, since from your drawing you don't want any blend over angled faces.
I do apologize but I'm not quite sure about your last question.
Are you trying to connect a Lerp into the Top, Middle and Bottom Tex ports of the Triplanar Sampler node? These ports can only have Texture Object nodes connected to them and unfortunately you cannot have anything but that connected to them.
Is it possible for you to give a bit of additional information on what you are trying to do?