Apps with 'File-system view' feature

rdiff-backup backs up one directory to another, possibly over a network. The target directory ends up a copy of the source directory, but extra reverse diffs are stored in a special subdirectory of that target directory, so you can still recover files lost some time ago.

OpenMTP is a free and open-source app to transfer files from an Android Phone to macOS.

K4DirStat, fork of KDirStat , is a small utility program that sums up disk usage for directory trees, very much like the Unix 'du' command. It displays the disk space used up by a directory tree, both numerically and graphically.