Compositing Workflow/How to compose a render after restarting Blender? I'm new to Blender (coming from C4D) and currenty working on an architectural visualisation like this:


The Image is a placeholder because I can't show the project.

I made three view layers


Clay Render
Texture Render
Freestyle Layer


After rendering I combined all the view layers to my final render and everything is fine.

After restarting Blender the render was gone. 

Now I need your help:


How do I continue working on a composition in Blender 2.80 after restarting? 
How do I save the Render with all passes and cryptomattes to work on
it later?
How do I compose multiple renders with the same composition node system? For example a different camera.


Normally I compose my images in Photoshop, but I want to try it in Blender, because it seems so much easier and quicker.

Thanks in advance!
I think what you are missing is the FileOutput Node.

here is a basic Setup for your 3 Layer.
check the docs for renderlayer in Blender and you are good to go.  

you can do a lot more then saving files with the compositing context, so have look and do some experimenting.