Super Dragon Ball Heroes' incarnation of Xeno Trunks originally almost achieved Super Saiyan 4.
A page of the Super Dragon Ball Heroes 9th Anniversary Super Guide was translated by user @Cipher_db on Twitter. He translated the passage as, "The original plan for Trunks: Xeno's super form was to go with Super Saiyan 4, but decisions such as what to do with the hair color ("Should it stay purple? Turn black?") led to it being scrapped in favor of Super Saiyan God."
First appearing in Dragon Ball GT, Super Saiyan 4 was used by both Goku and Vegeta, resulting in their hair growing long, but without changing into the golden color normally associated with the various states of Super Saiyan. This would have caused issues, as Trunks has purple hair, like his mother, Bulma.
Super Dragon Ball Heroes is an arcade trading card game that launched in 2010. A web series of the same name inspired by the game and set after the events of Dragon Ball Super released in 2018. In both, "Xeno" is used to refer to versions of characters from other timelines that are members of the "Time Patrol," which works against the Dark Empire and to protect the integrity of the timeline.