The 3DS version lacks this object editor, due to technological constraints. According to game designer Jeremiah Slaczka, the Wii U version of the game can store more than 900 custom objects.

Customized objects can be named and saved - typing in the name of a saved custom object allows it to be spawned at any time. Players can also customize their objects with scaling and coloring tools, similar to another 5th Cell franchise, Drawn to Life. Furthermore, there are numerous properties that can be assigned to objects, such as movement and offensive capabilities. As well as the adjective system that was introduced in Super Scribblenauts, players can now attach multiple objects to each other for example, creating a dog with wheels. The game was built on an upgraded version of the Objectnaut engine, providing the player with several additional options when creating objects. Due to the additional power of the Wii U, a budget meter is no longer present allowing up to 60 objects to be displayed at the same time. There are also male and female versions of all NPCs (including animals) now, as well as new functions for the time and arcade machines. There are now also smaller challenges within the world that reward the player with Starite shards - collecting ten of these shards is another way to earn Starites. Sometimes, this will transport the player to a self-contained level, much like earlier Scribblenauts titles, where the player must solve multiple puzzles before being awarded with a Starite. Players can traverse different themed areas and accept challenges from NPCs. One of the primary differences with this game is that it takes place in a large overworld that is open to exploration, as opposed to the first two games in the series, where the player had to choose an individual puzzle to earn Starites. Scribblenauts Unlimited is more adventure-based than Scribblenauts and Super Scribblenauts. Maxwell returns as the playable character and the objective is still to collect Starites by using objects the player creates to complete various tasks. The core fundamentals of the gameplay in Scribblenauts Unlimited are similar to previous entries in the series. Now he must go across the Scribblenauts world to help the people, collect the Starites, and save his sister. The mysterious old man has put a curse on Maxwell's sister, Lily after his prank gone wrong.

Scribble nauts unlimited gameplay