When the Option key is pressed in Excel for Mac, numbered and lettered labels appear over the ribbon tabs and Quick Access Toolbar icons. These labels are a visual aid for keyboard navigation and disappear upon pressing the Escape key. This behavior is specific to Excel and does not occur in other Mac applications like TextEdit or Finder. The user is running Excel version 16.77.1, which is reportedly no longer supported. Several troubleshooting steps have been exhausted, including checking system accessibility settings, input monitoring, and background processes. Excel's own accessibility preferences and add-ins were also reviewed without success. Crucially, the "KeyTips" setting, which typically controls this feature, is absent in the user's Excel version. The user has also examined Office preference files via Terminal for relevant settings without finding any related keys. The question posed to support is whether this is a known issue in unsupported Excel builds and if there's a way to disable it, or if a reinstallation is necessary.