Okey beta version 0.7.1 of ScheduledRestart is released. To install it on Volumio go to your http://ip-of-volumio-instance/dev and set Plugins Test Mode to enable.
You could now install ScheduledRestart from plugins and then System tools.
If you set a new schedule and save it the log output should show something like this:
info: CoreCommandRouter::executeOnPlugin: scheduledrestart , saveSchedule
info: Saving schedule with data: {"hours":{"value":4,"label":"04"},"minutes":{"value":20,"label":"20"},"monday":true,"tuesday":true,"wednesday":false,"thursday":false,"friday":true,"saturday":false,"sunday":false}
info: Scheduling reboots with hours: 4, minutes: 20 in timezone: Europe/Amsterdam
info: Scheduling job with cron expression: 0 20 4 * * 0
info: Scheduling job with cron expression: 0 20 4 * * 1
info: Scheduling job with cron expression: 0 20 4 * * 4
info: Schedule saved successfully. Reboot schedule updated.
Please report any bugs or errors.