Each LaunchRivals account connects one Steamworks account at a time. That one key already covers every game on the Steamworks account, so most studios never need more.
Pasting a different key replaces the one that is connected. Numbers already loaded stay, and from then on new numbers come through the new key.
A game shows "not part of this Steamworks account" on the settings page when it sits in a different Steamworks account than the key you connected.
Your games are spread across several Steamworks accounts, for example some self-published and some with a publisher? Contact us, tell us how they are split, and we will help you find the best setup.
Tip: on Studio, your teammates see the connected sales and wishlists too, without a key of their own.