Google script to list (on a Google Sheet) all files shared in your google drive, including all viewers, editors, and sharing permissions. Credit goes to @woodwardtw (https://gist.github.com/woodwardtw/22a199ecca73ff15a0eb) as this is an improvement on his code which only assesses a single folder and one level of sub-folders down.

whatFilesHaveIShared.gs

function listFolders(folder) {
     var sheet = SpreadsheetApp.getActiveSheet();
     sheet.appendRow(["Name", "Sharing Access", "Sharing Permission", "Get Editors", "Get Viewers", "Date", "Size", "URL", "Download", "Description", "Type"]); //writes the headers
     
     //var folder = DriveApp.getFolderById("INSERT_YOUR_FILE_ID");//that long chunk of random numbers/letters in the URL when you navigate to the folder
     //getLooseFiles(folder, sheet);
     //getSubFolders(folder, sheet);
  
     //instead of getting folder by ID rather get all folders and cycle through each. Note this will miss loose files in parent directory.
     var folder = DriveApp.getFolders()
     while (folder.hasNext()) {
         var name = folder.next();
         getLooseFiles(name, sheet);
         getSubFolders(name, sheet);
      };

 }

function getLooseFiles(folder, sheet) {
     var files = folder.getFiles();//initial loop on loose files w/in the folder
     var cnt = 0;
     var file;

     while (files.hasNext()) {
         var file = files.next();
         var listEditors = file.getEditors(); //gets the editor email(s), doesn't show your own as it's assumed
         var editors = [];
         for (var cnt = 0; cnt < listEditors.length; cnt++) {
             editors.push(listEditors[cnt].getEmail());
             Logger.log(editors);
         };
         var listViewers = file.getViewers(); //gets the viewer email(s)
         var viewers = [];
         for (var cnt = 0; cnt < listViewers.length; cnt++) {
             viewers.push(listViewers[cnt].getEmail());
             Logger.log(viewers);
         }
         cnt++;  //data chunk pushes all the file info to the ss

         data = [
             file.getName(),
             file.getSharingAccess(),
             file.getSharingPermission(),
             editors.toString(),
             viewers.toString(),
             file.getDateCreated(),
             file.getSize(),
             file.getUrl(),
             "https://docs.google.com/uc?export=download&confirm=no_antivirus&id=" + file.getId(),
             file.getDescription(),
             file.getMimeType(),
         ];

       if(data[1] != "PRIVATE") {
         sheet.appendRow(data);
       }

     };

}

function getSubFolders(folder, sheet) {
var subfolders = folder.getFolders(); //same thing as above but for all the subfolders in the folder

     while (subfolders.hasNext()) {
         Logger.log(folder);
         var name = subfolders.next();
         getLooseFiles(name, sheet);
         getSubFolders(name, sheet);
     };
}

To use:

• Create a new google sheet
• Select Tools -> Script Editor
• Copy the code over
• Save and run (click the play button)