Unable to get events for shared files

So is there a way to get the cursor for "shared files" ?

No, unfortunately there isn't a way to get a cursor/longpoll for shared files from another account like that exactly, but I'll pass this along as a feature request. I can't promise if or when that might be implemented though. It's only possible to monitor changes actually in the connected account.

According to this article by Dropbox https://dropbox.tech/developers/manage-team-sharing-in-your-dropbox-app
It says to
1. Create a new app from your App console
2. Select ‘Dropbox Business API’
3. Select ‘Team member management’

That post is old and out of date now. You no longer need to register a Dropbox Business API app with a specific Business permission, such as "Team member management" or "Team member file access" like that. You should instead just register a "scoped" app with the "Full Dropbox" access type, which can be used to access both user and team (Business) functionality, by enabling whichever scopes you need. 

For example, to connect to a team and use the "Member file access" feature to access the files of any member of the team, you would enable the "team_data.member" scope.

A workaround would be force 'unhiding' of target option (Team member management).

Do not modify the Dropbox web site. Any result of doing so would not be officially supported. Please use the "scoped" app functionality as described above to enable access to whatever features you need.