Compositor: how to save output node files when I wish to

Lots of posts, searches and possible answers but I still cant save image files as I would.
The only way to make the output node to work is just RENDERING again. And

If I render and use “esc” it wont save (and I often skip the render when samples are enough)
If I tweak nodes after the rendering it wont save.

Please help me, I would like to tweak compositor nodes and getting the output updated again.