Is there a way to query a list of all files shared externally across all users? If not, is there a way to do this on a per user level?
Unfortunately, there isn’t a Dropbox API endpoint that can query a list of all shared files externally across all users, but I'll shall pass this along as a feature request.
Currently we have the following Dropbox API endpoints that can list shared files received by the account, shared folders accessible to the account, shared links created by the account, and retrieve information about accounts connected to individual shared files.
Listing shared files that the account has received
Listing shared folders that the account has access to
Listing shared links that the account has created
Listing accounts connected individual shared files
Please note that to locate files shared with other accounts, you will need to implement the /2/files/list_folder and /2/files/list_folder/continue endpoints with the parameter include_has_explicit_shared_members: true.
Based on the above endpoints you should be able to execute them on behalf of your team members individually by passing a Dropbox-API-Select-User HTTP header with the team_member_id to act as a specific member.