That's the only slot where you can find them cards from the bonus sheet aren't found in the wildcard or traditional foil slot in Play boosters
While Pia Nalaar, Chief Mechanic would be right at home in any Artificer deck you might decide to build, it'll be key to see what kinds of artifact creatures are in the Living Energy decklist to judge the feasibility of this as the Commander within the precon
Sword of Truth and Justice, Karn's Bastion, and Throne of Geth can help you have continuous proliferate resources to keep Idris on the battlefield
Then the active player gains priority for the first time
PS: maybe an idea for finding the missing cards: compare the LQ images downloaded by Forge with your images (comparing the same directories like "4E", "5E", ...)
As you open your Play Boosters, sort your cards by color, placing any multicolor, colorless, or land cards into their own piles