to sort files by date, then name, you can first click on the "name" column, then on the "date" column.
I don't think that works in a custom model (or even in the off-the-shelf QSortFilterProxyModel) - unless the model (or proxy) implements such multi-column sort behavior. How does a standard QSortFilterProxyModel know to maintain the sort on one column that contains duplicates while sorting a second column with respect to those duplicates? As far as I have seen, sorting on any column occurs independently of other columns and results in all rows being reordered solely on the sort order of the chosen column.