In this blog, we will see how to edit the default User Profile List. By default, SharePoint does not provide a direct way to edit this hidden list.
Accessing the User Profile List 
https://RKSite.com/teams/RKDevSite/_catalogs/users/detail.aspx 
<<Site Url>>/_catalogs/users/detail.aspx
Steps to edit the User Profile List
- Get the GUID of the list.
- Form the URL to edit as a normal list.
 
Step 1
The below CSOM application code will help you in getting the GUID of the User Profile List. Create a console application and add CSOM NuGet package and replace the below code in Program.cs file.
- using System;  
- using System.Collections.Generic;  
- using System.Linq;  
- using System.Security;  
- using System.Text;  
- using System.Threading.Tasks;  
- using Microsoft.SharePoint.Client;  
- namespace UserProfileList {  
-     class Program {  
-         static void Main(string[] args) {  
-             string siteUrl = "https://RKSite.com/teams/RKDevSite";  
-             using(ClientContext context = new ClientContext(siteUrl)) {  
-                 SecureString securePassword = GetSecureString( << Password >> );  
-                 context.Credentials = new SharePointOnlineCredentials( << UserName >> , securePassword);  
-                 List oList = context.Web.SiteUserInfoList;  
-                 CamlQuery camlQuery = new CamlQuery();  
-                 context.Load(oList);  
-                 context.ExecuteQuery();  
-                 Console.WriteLine(oList.Id);  
-             }  
-         }  
-         public static SecureString GetSecureString(string userPassword) {  
-             SecureString securePassword = new SecureString();  
-             foreach(char c in userPassword.ToCharArray()) {  
-                 securePassword.AppendChar(c);  
-             }  
-             return securePassword;  
-         }  
-     }  
- }  
 
 
Step 2
Once you get the GUID, build the URL as below.
https://RKSite.com/teams/RKDevSite/_layouts/15/listedit.aspx?List=77dffdaa-e518-1234-a1e4-8bb568fa22b6 
<<SiteUrl>> /_layouts/15/listedit.aspx?List=<<ListGUID>>
Here, the highlighted code is List GUID. Hope this blog will help you in coding.