I don’t know why it’s not showing up in the launcher, but you should still be able to find your 4.23 installation, go to the Engine/Binaries/Win64 folder and run UE4Editor.exe.
I don’t know why it’s not showing up in the launcher, but you should still be able to find your 4.23 installation, go to the Engine/Binaries/Win64 folder and run UE4Editor.exe.