Hmm?

I'll have to think about that, if you want to add the same name twice then there is no point in having diminishing validation lists.

1/. How many shifts do you have in a working day?
2/. Are all lines running at any one time?

If we can allow more than one entry per day then we could flag the log to indicate shifts or break-downs/down time, then produce tables to indicate each scenario,
i.e.
One table plus a break-down table for each shift, that would be quite do-able using the code to date. Maybe a sheet per shift and still only one common Log sheet.
I'm thinking out loud.