Timer-event start the process ever work hour in workdays
Bonita platform uses http://www.quartz-scheduler.org/ to handle BPMN timers. This means that you can use CRON expressions that are supported by the Quartz Scheduler.
The following page can help you generate a CRON expression that can do that. https://www.freeformatter.com/cron-expression-generator-quartz.html
0 0 8-18 ? * MON-FRI *
Put this expression in the timer condition (cycle) of your start timer event.