Regression as this used to work on earlier releases.

1. Add scheduled trigger
2. Edit schedule
3. Select Cron
4. Add expression like: 0 55 * ? * *
5. Done
6. Shows up properly on display
7. Save trigger
8. View trigger - switched to a daily every hour
9. Edit schedule - Daily selected, every hour, minutes are not shown or editable

Update: it's just a display issue, underlying cron is saved and interpreted correctly.
Workaround: switch to cron view to see the actual expression.