How do I create a link to a file in a different folder so that the user sees the file in different folders, but in fact it was the same file?
I think it is not possible.
But you can install the app “link editor” and link to a subsubfolder
e.g. for a subsubfolder path1/path2:
https://cloud.server.tld/index.php/apps/files/?dir=/path1/path2
In the link settings you can activate open in same window and not keypress for open it.
Sorry. It do not really solve your problem. Perhaps there is a better app.
Do you find a way to resolve your question ?
Is your question about online Nextcloud or synchronized Nextcloud on local folders of the users ?