Downtab 0.4.2

Fixed

• Switcher: holding Tab, or the Window shortcut key, with the Modifier keeps moving the selection like the native switcher, stopping on the last app or window; with ⇧, on the first. Separate presses still wrap around.
• Only one Downtab runs at a time: opening another copy while one is running shows Downtab is already running with the running version and location, and the new copy quits. Quit the running Downtab first to switch copies.