Make the time off Tool Tip more visible in the Resource Planner and the Workload Balancer for manually assigned work. When someone is assigned work during this time, a tool tip appears informing the user you have scheduled time off only when assigning work in bulk assignments. No tool tip appears in the Workload Balancer if a person has scheduled time-off and is assigned work. To the user it looks like work is assigned to a user without regard to having time off.
