I seem that you will not be able to run simultaneous quizzes without using CSV file.
When you create multple threads without using the CSV file, all theads may use the same username.
At the Moodle system, one user cannot have multiple sessions.
In fact, you can log-in to Moodle site with the same username via multiple PCs and multiple web browsers.
In such a case, each PC or browser have different session string.
However, whenever you do something with any of your PCs or browsers, Moodle system will assume that you are accessing it via your most recently used PC or browser.
Note that a single user cannot have multiple sessions at the same time within the Moodle system.
So that, a single user cannot use multiple login sessions at the same time.
As a result, many threads have failed to log-in in your test.
(Please see, labels 68 and 70 in test result image you posted earlier.)
If a thread fails to log in, the web page it received does not contain the "sesskey" value.
Threfore, the thread cannot get "sesskey" value.
Similarly, a single user cannot pretend to be multiple people and take a quiz at the same time.
If multiple threads use the same username, when one thread starts taking a quiz, other threads are forced to end.
(Please see label 68 and 70 in test result image you posted earlier.)
So that, all threads in your test failed taking the quiz.
(Please see label 116 in test result image you posted earlier.)
In conclusion, there is no successful way to proceed with the test without using the CSV file.
If you want to successfully run the load test, enroll the users included in the CSV file as member of your Moodle course.
Then, you should use the CSV file for load testing.
When you create multple threads without using the CSV file, all theads may use the same username.
At the Moodle system, one user cannot have multiple sessions.
In fact, you can log-in to Moodle site with the same username via multiple PCs and multiple web browsers.
In such a case, each PC or browser have different session string.
However, whenever you do something with any of your PCs or browsers, Moodle system will assume that you are accessing it via your most recently used PC or browser.
Note that a single user cannot have multiple sessions at the same time within the Moodle system.
So that, a single user cannot use multiple login sessions at the same time.
As a result, many threads have failed to log-in in your test.
(Please see, labels 68 and 70 in test result image you posted earlier.)
If a thread fails to log in, the web page it received does not contain the "sesskey" value.
Threfore, the thread cannot get "sesskey" value.
Similarly, a single user cannot pretend to be multiple people and take a quiz at the same time.
If multiple threads use the same username, when one thread starts taking a quiz, other threads are forced to end.
(Please see label 68 and 70 in test result image you posted earlier.)
So that, all threads in your test failed taking the quiz.
(Please see label 116 in test result image you posted earlier.)
In conclusion, there is no successful way to proceed with the test without using the CSV file.
If you want to successfully run the load test, enroll the users included in the CSV file as member of your Moodle course.
Then, you should use the CSV file for load testing.
(In our test plan, I have set up to use the CSV files for load testing.)
At first, I expect you to proceed with the load test according to user's manual.
Then, if you want to create your own test plan, you should look more carefully at our test plan file.
The mechanisms for getting "sesskey", "attemptid", and "qubaid" is described in the test plan file.
The mechanisms for getting "sesskey", "attemptid", and "qubaid" is described in the test plan file.