Horizontal sharing / selective sharing exceptions?

Hi there,

“vertical” sharing of folders in nextcloud is working superfine for me: i will define a folder an folder structure, set the top-folder to be shared with some users or usergroups etc…

However, once in a while, there will be a subfolder or some files WITHIN this structure, which i dont want to share with some person or some group of users.

Is there a way, to selectively exclude the sharing of some subfolder or files with a user or a usergroup which has been otherwise assigned to have the folder shared?

Or are there certain tags or colours or whatevery which i could assign to exclude the files from being shared, as an exception?