In one area you:
Define Weekdays as a day type to which you assign Monday through Friday
Decide that the area has additional events on Friday and, therefore, define Friday as a day type. You assign Friday to it, thereby removing Friday from Weekdays
Do define Saturday and Sunday as None. "None" has no schedule.
The Action Calendar will display
Weekdays as Monday through Thursday
Friday as Friday
Saturday and Sunday are None.
At this stage of your planning, you may decide to:
Create another area where you:
Create Friday as a day type and schedule the additional events,
Keep the day type Weekdays as Monday through Friday in this area.
Keep Friday as a day type in this area with a schedule that includes all the events for Weekdays and Friday's additional events. Action See "Configuring the Action Calendar – Copying Day Types"