The way that compositor works actually sucks. Today I try to use denoise node with a AO baked texture, to test it, and you can’t do a simple operation like that easily. If you don’t do a render (when you don’t want any render) you can see the composite solution because potato. But also you need to do a node conection, because if you made a render but not connect render with output the composite don’t work…
This part must be redone from a UX pov
click ctrl+shift+click to use the viewer node. and set the image editor to viewer node. (See the image layout above)
Does this works for your workflow?
Thanks, It improve the workflow, but still being hard to understand the behaviour of the compositor. If I had problems with it after a decade using blender