I want to make a backup with multiple schedules, for each weekday. Is
there a way to make it automatically append the day of week to the backup
filename, like backup-MON, backup-TUE, backup-WED, etc. (The backup
files are overwritten each week, but at any time, I have the backups of
the last 5 weekdays.)

I guess I could make 5 different backup jobs and give the filename I
want, but it's a pain. Plus if I need to make changes (add or remove
folders to the job), I have to go through all 5 jobs.