gelöschter externer Editor

Easy way- Delete the external editor listing using File Explorer. To be found in a Lightroom folder like-

C:\Users\{YourName}\AppData\Roaming\Adobe\Lightroom\External Editor Presets.

The less easy way is- Choose the (uninstalled) External editor preset in the LrC Preferences tab, click the preset dropdown menu and select [Delete Preset 'xxxxx'...]