“Authentication Required” type proxy connections are now supported in Toad.
So, with this kind of set up:
create user app_user identified by app_user_pw;
create user end_user_ar identified by end_user_ar_pw;
grant create session to app_user;
grant create session to end_user_ar;
alter user end_user_ar grant connect through app_user authentication required;
You would connect in Toad like this:
Note that SQLPlus does not allow these types of connections, so if you attempt to launch SQLPlus from this kind of connection in Toad, it will fail.