DiffMate ‑ Asset Compare Tool

It does let you get an overview of what files have changed, but the diffing algorithm is very poor. If a block of code changes from multi-line to single line, it throws off the diff for the rest of the file. See what algorithm VS Code uses, and use that; they have excellent blog posts on diffing.

I ended up exporting the themes and comparing in VS Code using the "Compare Folders" extension.

I also cannot find a way to undo individual changes to files. If I accidentally merge a change to the wrong side, or merge the wrong change, I have to discard all changes and start again.