How to make multiple displacements map node thanks in advance for any help.
Sort of a beginner but also not. Just haven't tried doing this before. 
So this is what I have done so far.
I took multiple images and put them in a rgb in photoshop. So now the 3 layers are over one another and I exported it as a TIFF file. 
There are 4 of the TIFF files.
So now what I want to do is to paint the 4 textures in blender onto an object. Take the unwrapped object, export it as one tiff. Back into photoshop and separate the rgb layers again to have one tiff instead of 4. 
So then once I have done that I will put it back into blender to have multiple layers to change the intensity as I would like it to be.

I truly hoped I explained it properly. My English sucks. So If you have any questions I would answer the best I can.

Thanks in advance for any help provided.

the displacement Im trying to replicate from texture xyz
https://texturing.xyz/pages/making-a-digital-face-sefki-ibrahim

1) Put images into rgb and crop the mouth forehead and nose part.



2) paint onto character



3) back to photoshop to seperate the pictures



4) use as displacement in blender

thats where I am now
test it with a cube and the method worked. Now I just want to know about nodes with multi displacement.

I havent baught the displacements yet. Im doing tests to see if its possible in blender because I havent found any tutorials on this. Only in other programs so Im trying to replicate. They are expensive so I dont wanna buy something I can do nothing with. 

So there will end up being 3 different displacements. I know how to put 2 but not sure with 3
If you paint an image on the model with texture drawing, it just copies all the texture channels into your target texture. It's totally up to you, what kind of information you store in those channels. You can paint even normal maps onto a model.
If the displacement maps are just grayscale images, you mix them with add, or screen (or whatever you want) blending, and then feed the result to the Bump node (or to displacement input of the material).
You even don't need to separate the colors of your painted colored image in the photoshop - you can use 'Converter\Separate RGB' node instead, play with the levels of each channel, mix them together, and feed that mixed value to the Height input of the Bump node, or to the Displacement input of the material output node.
And images on your link are enough to play with to have an idea. If you want, you can paint some scratches with white and black brush (50% gray = no displacement) to see how it affects the look of the surface of your mesh.