In Nemo (from Cinnamon) when you change a folder icon, the file manager opens the folder in question to look for an icon. Dolphin doesn't quite to that nor does it remember a icon folder location either (defaults to home) and it is really hard to change a lot of icons to some random icon you have. I am obviously referring to using custom icons not found in the icon theme used by the system.
So you would like the file picker to default to the current directory, not the user's home folder?
From quickly checking: https://cgit.kde.org/kiconthemes.git/tree/src/kiconbutton.cpp#n160 does not open the KIconDialog with the currently selected icon. Maybe using setCustomLocation() for icons with a path helps.
Hm, that's for KIconButton, but dolphin probably directly uses the KIconDialog.
Would be nice to have the options to: 1. open the folder the icons is changed for 2. open some other folder that user wants (have a setting for this). Or at least default to the last used folder for icons.