On my TW/KDE system when I open a file dialog in an application all the file dialogs display the files and directories in name order and do not group the directories first, I’d like to change this so that all file dialogs display the directories first followed by the file, each in name order but so far I’ve not found any way to achieve this.
As far as i know there is no unique answer to your question.
On my system most KDE applications (e.g. KMyMoney) use the standard KDE file open dialog which shows a button on the top that will allow you to customize the sort order.
Firefox (which is not a KDE application) uses as different file open dialog (i don’t know how to configure the sort order there) and LibreOffice allows you to choose between the LibreOffice and the standard KDE file open dialog.
Probably there are other applications which bring their own file open dialogs or use file open dialogs from other DEs.
So probably it’s best you specify which applications file open dialog you want to customize.
Thinking about it I believe Firefox/Waterfox and Thunderbird are the main culprits and obviously use their own dialog, that’s a PITA because I think not allowing fully customisation or switching to KDE dialog is plain wrong. Most others I’ve tried so afr seem to follow the KDE standard which is what I expect to have.
Reading between the lines it would appear that the Firefox code is patched for openSUSE but I dont normally use Firefox I use a clone Waterfox so I doubt that kmozhelper will do anything for that. Pity Mozilla dont use QT or supply a version which does, or use normal KDE file menus.
I can confirm that Firefox works as expected with the normal KDE open file dialog. The issue is that it does not work with Firefox clones like Waterfox and I suspect this cannot easily be fixed. This also explains why my Thunderbird does not use the KDE dialog because I use an older version installed manually not the system version as that does not support extensions I will not work without.