Keeping blank date cells separate without sorting by the existing dates

Hi,

I have a list of members and a column of dates when they paid their membership fee. Some have not paid yet, so the cells are empty. Now I want to sort the list so that the entries with a blank date are kept separate but the whole list can be sorted by the names. This makes it possible to see who has paid, keeping the names in alphabetical order in both blocks.

I'm attaching several versions of a small sample file.
Sorting blank dates_0.xlsx shows the initial, unsorted state.
In blank_dates_1.xlsx the rows are sorted first by date, then by name. This keeps the blanks as a block at the bottom, but the sorting by date takes priority, and only the blank cells are sorted by name.
In blank_dates_2.xlsx I have applied a "dirty trick" to achieve the desired result: All but the filled cells have a very dark grey as their text color, the filled ones have "Automatic". Sorting that column not by values, but by text color does the trick: The rows with filled as well as with blank dates are sorted by name, while keeping the blocks separate.
However, this means that whenever someone pays and I fill a cell, I need to change the text color afterwards.

Does anyone know a more elegant way how to achieve this result?

Thanks,
Tohm59