bde-lock is a simple Windows installer hosted on GitHub, which creates a drive context menu entry Bitlocker Lock Drive to lock an unlocked BitLocker encrypted drive without the need to restart the Windows system. If an encrypted drive is (automatically or manually) unlocked during Windows startup or operation, there is no drive context menu entry to lock it again. To do this, one can run either

manage-bde.exe -lock Drive:

in a command shell or

Lock-BitLocker -MountPoint Drive:

in a powershell. To add the first command to the drive context menu, a few registry keys are required. To spare other users the manual work I created the installer using an NSIS script, which will create the registry keys to add the context menu entry and run the necessary command with elevated permissions. If no longer required an uninstaller will remove all created or installed content.