Re: how do I configure Scan Multibranch Pipeline Triggers for a specific time every day?
Uncheck "Periodically if not otherwise run" as that won't do what you are wanting to do. Look at the other options or sections.
Periodic selecting 1 day, will execute the job daily but you won't have control over when in the day it will run, also if something else triggers the job then it won't run as it says "if not otherwise run". A hack would be to select 1 day, then at midnight manually trigger the job, then it should execute about midnight going forward if no other builds are triggered.
What you are describing is the cron option, which in the UI is shown as "Build periodically" and I entered "H 0 * * *" will trigger the job between midnight and 1am.
Without seeing more of your configuration, or instructions on how you created your job, then I can't help you more.