Hi Maria!
Thank you for your reply and explanation. I came to the same conclusion a couple of days ago, but thank you for confirming the options.
It seems that, in a quiz with several scenes, it's either one timer that covers all scenes and slides (also any intro or transition slide) or separate timers for each scene, which you can then set to start with each first quiz slide. The reason why I was interested in having several scenes/quizzes was to obtain separate results for each of the six content sections of the quiz. However, I realized this was overcomplicated and that there was an easier solution.
For my particular case, I solved it by putting all the slides into one scene. This allowed me to resolve the timer issue, which I set to start with the first quiz slide. Then, I added several results slides, one for global results (let's call it A) and several others (B, C, D, E, F, G) for each section. The only one to where the learner can navigate is A when they finish the quiz. Results slide A calculates a score for all quiz slides. The other results slides (B to G) are not linked from anywhere else and are there to calculate the scores of the six sections, which I then copied and pasted to A for a section breakdown. In B to G, I calculate the score of only selected questions pertaining to those sections.
I'm not sure my explanation was great, but hopefully it can help anyone who might experience a similar issue.
Thank you again for your follow-up!