External Storage (SMB) - Nextcloud-App

can someone tell me how does External Storage app, configured to sync with a folder on another NAS (in my case Photos), work with Nextcloud-App on both Windows or Mac?
If I don’t check the box beside the folder in the App, I don’t see it.
If I check the box, it will probably sync everything down, which wouldn’t be what I’d like.

What I would prefer is a configuration in which Nextcloud has the folder Photos, but does not copy down the files, rather access them only on the remote NAS, much like it would do when accessing the share directly (which I can do, but it would be nice to have it visible in Nextcloud).