I need to do that for FOLDERS. The use in Dropbox was only a example. If I choose any folder in the folder hierarchy in the popup menu from proxy icon in title bar in ANY window, a Windows 8.1 Pro VM (from VMware Fusion) starts. In any folder in any window title.
How do I choose the selected app for open in folder properties? (to re-choose Finder to open folder file:// links in any app).