Does not match your requirements exactly, but may come close (source and auto rebuilt PDF side-by-side with synctex to jump from one to another, etc) - VSCode with LaTeX Workshop extension. Not sure what VSCode can do for inline editing of images—but perhaps there is an extension that can help. It is capable of collapsing/expanding sections/subsections in the source view, and I think it does have a tree-style outline editing in a side-pannel too.
Does not match your requirements exactly, but may come close (source and auto rebuilt PDF side-by-side with synctex to jump from one to another, etc) - VSCode with LaTeX Workshop extension. Not sure what VSCode can do for inline editing of images—but perhaps there is an extension that can help. It is capable of collapsing/expanding sections/subsections in the source view, and I think it does have a tree-style outline editing in a side-pannel too.