Thank you. I tried it and found what looks like a bug: After expanding the top level item, modified files lose their "action icons" - in my case, an upward facing arrow. The arrow is present after expanding the top-level item, but goes away Select All then Right Arrow.
If not for the bug, this would be a good workaround if there was a way to: a) expand recursively (I have six levels of directories), and b) hide unchanged files.
Too bad.