Show Detailed Tree View by default in KDirOperator. This only affects the file open/save dialogs, because all other clients set their preferred view mode manually (checked with lxr and submitted patches that have been accepted for the two that didn't).
This change will result in Open & Save dialogs displaying Detailed Tree View by default instead of Simple View.
Detailed Tree View is better for content that is optimally located by its filename or metadata, which I would wager is more common, so it should be the default view. Also, bandwagon argument: Windows and GNOME both display the same view by default in their Open/Save dialogs now (macOS displays the navigation-friendly {Column View} by default, which sadly lacks a KDE equivalent).