Hi there. Accounts cannot be merged or transferred. That is not a service offered by Bungie or Sony. If you want to use a different PSN account with Cross Save, you would need to disable Cross Save, unlink the PS4 account from your profile, link your PS5 account, and wait the mandatory 90-day cross save security cooldown before you can activate Cross Save again with your desired PS5 account. To learn more, read the [url=https://help.bungie.net/hc/en-us/articles/360049498031-Destiny-2-Cross-Save-Guide]Cross Save Guide[/url].