Preferences: File browser for search and startup paths
It would be nice if at least the "New" path buttons would open a file dialog for the user to select a directory.
Concrete user impact: If you're in a classroom and guiding the students through configuring an installation, it's easy to tell them to "click New and navigate to the place where you put the externals/abstractions." It's quite a bit harder to explain to them that they have to find the directory in the Finder, right-click-hold-and-add-the-option-key and Copy Path. (In Linux and Windows, copy-as-path is not hidden, but "friendly" MacOS makes this unnecessarily hard.)
(For that matter, where are the paths stored? If you have to add several search paths, the Preferences dialog might actually be less convenient than opening, say, a JSON file and adding paths by hand. Or, if you're administering a digital media lab and you need to set up 20 identical installations, why not just copy a prepared preferences file?)