The tray icon

AltTab has no window of its own when it is idle — it lives in the notification area.

The tray menu

About AltTabVersion, build, and a Copy details button for bug reports. Also Shift+F1.
ReadMe, Help, Release NotesThe three documents shipped beside the executable. Help is this document; F1 opens it too.
SettingsThe Settings dialog. Also F2.
Disable AltTabTurns the hotkeys off without exiting. See below.
Check for UpdatesAsks now, whatever [General] CheckForUpdates says.
Run at StartupRegisters a scheduled task so AltTab starts with Windows.
Always run as AdministratorThe same task, with highest privileges, so the hotkeys reach elevated windows. See troubleshooting.
Close All WindowsEvery window in the list. Asks first.
Reload AltTabSettings.iniRe-read the file. Only needed if the automatic reload has not noticed; AltTab watches the file.
Restart, Exit

Two click gestures

Single clickOpens the switcher.
Double clickToggles Disable AltTab.

One button with two gestures has an awkward consequence worth explaining, because it is visible: Windows delivers a double click as click, double-click — the first click arrives before the second exists. So the single click's "open the switcher" waits for the system's double-click time before acting, and a second click cancels it. That means a tray click opens the switcher a fraction of a second later than you pressed it.

The alternative — open immediately, toggle on the second click — shows the switcher for a few hundred milliseconds and then disables the application, which reads as a glitch. The tray icon is the switcher's secondary way in, so the small delay is the better trade.

Disabled

Disable AltTab is for the times something else needs Alt+Tab — a remote desktop session, a game, a recording.

While it is disabled:

Double-click the icon, or use the menu item, to bring it back.

It is not remembered. DisableAltTab lives only for the session: it is never written to the INI, and restarting AltTab — or reloading the settings file — comes back enabled.

Hiding the icon

[General] SystemTrayIconEnabled removes it. The hotkeys keep working, but with no icon there is no menu and no way to reach the settings except F2 in the switcher, so know that gesture before you turn it off.