The above Game Launcher solution didn't work for me on my Note 8, but this did:
1 - From the Home screen, slide up your list of apps.
2 - Open “Home Screen Settings“.
3 - Select “Hide Apps“.
4 - Go through your apps and select which ones are currently hidden, just as if they weren't hidden but you wanted them to be.
5 - Come out of Apps section
6 - Go back into your apps, then repeat steps 1 to 4, but this time deselecting the apps you had 'hidden' to un-hide them.
7 - They should now all appear in Apps.
I hope that helps. In my situation I had just used Smart Switch to upgrade to the phone, and so it may have caused some errors along the way and hidden some things without marking them as hidden.