Did you restart the switch after? i think it will show the free space once you do that. I am not sure though, can't quite remember, but give it a try.
You need to exit Goldleaf and enter it again to see any difference.
Try delete from data management or reinstall then redelete
When you say it's not showing in Data Management, did you check the very bottom of the list? When games fail to install for me, Horizon reports that the space is taken up, but doesn't report the game file's correct size, so it gets sent all the way to the bottom and has a gray icon as a picture.It's not showing up in goldleaf or data management. Will the reinstallation overwrite the old one? Because I don't have enough space to install 2 copies of the game side-by-side. My SD is almost full.
This worked for me..Deinstalling / Deleting another software with nintendo's built in software management solved the issue. It freed the space from the previous programme, deleted through goldleaf.