This is still cool, though. It’s a built-in diff tool! I use WinMerge when I need to compare two files kinda ad hoc on Windows (kdiff3 for “real” diffs on macOS and Windows), but didn’t have a similar tool for macOS.
Except I did.
1. Open two documents (in my case, style.css in both the original and modified parent theme) that you’d like to compare
2. Click View > Show Files or type CMD + 0. This will open a sidebar with all opened documents.
3. Highlight the 2 files you want to compare in the Documents drawer, right click on them and select the option ‘Compare‘.