This is how to move the Launcher.
You can use a symbolic link to the new location. A symbolic link is totally transparent to the filesystem and any program. (Don’t confuse it with a simple link or otherwise called a "shortcut) There is an old blog post -view it here- about moving the vault out of the launcher to gain space in Windows system disk / partition (C: usually) Since then the vault can be moved from the launcher configuration settings, the gear wheel at the top right.
But I figured why create yet another Epic Games location, why not move the whole Launcher and gain that much extra space, for which job the symbolic link remains an elegant solution.
For this example the installation was typical UE4.16.2, meaning “Epic Games” (containing the Launcher) folder directly under C:\ and the Engine executables, binaries and program files, under “C:\Program Files” So modifying the instruction set from the old blog instructions :
-
go to your [GameEngineInstallFolder] eg."Epic Games", container folder, eg. C:\ -
copy the folder to the desired position (other drive, network storage), eg. D:\Epic Games -
rename original to something else, eg "C:\bak.Epic Games" (delete later, better safe than sorry) -
start the cmd.exe (terminal) with administrator privileges (right mouse, start as admin) -
change directory to original [GameEngineInstallFolder] container, eg. C:\ -
in the old location, create the symbolic link to your new location, e.g. (in C:\ enter the command: mklink /D "Epic Games" “D:\Epic Games"
That’s it!
The new location is transparent to the file system (it “thinks” it’s still in C drive), so do not change any shortcuts to the Launcher executional, either pinned on your Taskbar, Start menu, your desktop or wherever else! These should still point to C:\ location, see the properties of my desktop shortcut, as an example :
Now delete the old VaultCache folder and free up your drive 
The engine is normally in the Program Files folder of Windows. Not sure how the symbolic link will work there.