Scheduled staff per interval

Hi All, newbie here seeking some advice

Attached is a schedule calculator I use for running shift scenarios, I punch the requirements from forecasting team into ‘calculator ‘ tab and then start building schedules on master tab. This is a simple ‘WhatIF’ calculator only problem is it requires a hugh amount of maintenance as I need to add new shift opens, example I have a 2pm-5:45pm shift option but not 2pm-6pm so to add I need to go in and add the shift and manually update the calculator. Wondering if anyone uses something similar? I would like to build a sheet that would allow any possible shift work hours. Haven’t been able to find anything so far.

Thanks in advance