Hello there!
Sorry, but you will have to wait the full 90 days. There is no way around this.
[quote]Cross Save is intended to be a one-time action, but we realize there may be cases in which you want to visit the characters you left behind. Once Cross Save has been disabled, you will have access to your original characters on each platform. [b]There is a 90-day wait to re-enable the feature. This policy exists to discourage activity like account recoveries by other players.[/b]
https://www.bungie.net/7/en/CrossSave[/quote]
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