It feels like only recently that Fortnite got a feature to merge your accounts between two consoles. But now, Epic has announced that the account merge feature for Fortnite will end permanently on May 6.
Epic's blog post about the end of the process notes that all pending account merges will still be completed at a later date, but they must be submitted before May 6. The account merge feature for Fortnite is where you can take your primary account on one device, say your PS4 for example, and merge your secondary account on another platform, for example the Nintendo Switch, with the primary account.
The Account Merge feature will be coming to an end on May 6, 2019. Be sure to submit a merge request prior to that date for any eligible accounts.— Fortnite (@FortniteGame) May 1, 2019
Note: Any "In Progress" Account Merge requests will be completed as long as they're submitted prior to May 6 https://t.co/PkxLcl5WnR
In doing this, your secondary account is effectively disabled. All V-Bucks and reward items that you earned on your secondary Fortnite account are then transferred over to your primary account, so you've basically consolidated your progress into one account, which can then be used across all platforms that Fortnite is available on.
You've now got a matter of days to submit two of your accounts for merging. Epic's website says that the full process can take upwards of a few days to complete, but as long as you get your submission in before May 6, you'll be fine.