The Regulation about examination and admission §7.1 states the following

"Re-sit examinations
Re-sit examinations among them final examinations are arranged for students with a
legitimate leave of absence from the ordinary examination. A legitimate leave of absence
is granted in documented cases of illness or other pressing reasons. A written application
for leave of absence must be submitted as soon as possible to the appropriate faculty dean
for approval."

Not attending an examination, without a valid reason, will count as one examination attempt.

Please check the "Examination registration" for your department to find out more about registration for elective courses/courses outside of the individual education plan.