How to remove default schedule from Employee's Work Schedule

We have set up a default schedule for all employees at Organization level. But approx 10% of employees needs different schedules. So, we tried loading those different schedules to those employees through HSDL and working fine. But Issue being faced is - the default schedule in the background is still showing up for those employees when we try to avoid loading schedule for any specific days (screenshot attached).

The ask is, can there be a shift created with 0 time, that can be used to schedule days off so that the default schedule doesn't appear when the employee is supposed to not be scheduled. - Tried creating a shift with 0 duration but system is not allowing it.