Open windows CMD in administrator mode (need admin since it’s making the symlink in a program folder).

Use this code to make a symlink to Epic Launcher in the Epic Launcher folder with a custom name based upon the game you are adding (in this example AlienIsolation.exe):

mklink "C:\Program Files (x86)\Epic Games\Launcher\Portal\Binaries\Win32\AlienIsolation.exe" "C:\Program Files (x86)\Epic Games\Launcher\Portal\Binaries\Win32\EpicGamesLauncher.exe"

Then add non-Steam game with:

Target =
"C:\Program Files (x86)\Epic Games\Launcher\Portal\Binaries\Win32\AlienIsolation.exe"

^^ that symlink we just made

Start In =
"C:\Program Files (x86)\Epic Games\Launcher\Portal\Binaries\Win32\"

Launch Options =
-com.epicgames.launcher://apps/8935bb3e1420443a9789fe01758039a5?action=launch&silent=true

^^this custom launch option code is what you see after inspecting the properties of the default shortcut Epic makes on desktop (plus a dash “ - “ at the front), this is what I saw for Alien Isolation but it’ll depend on the game

Now you can add as many Epic games the require the launcher as you want, just be sure to close the Epic Launcher after you’re done playing to clear the Steam overlay and running game from the Epic Launcher and Steam.