It is impossible to turn off Tree View expand/collapse animation in System Settings. Turning off Animation in Oxygen or Breeze widget style keeps Tree View animated. Workaround for this issue: 1. compile and run https://sourceforge.net/projects/qt5ct/ QT_QPA_PLATFORMTHEME="qt5ct" qt5ct 2. Interface tab -> reenable 'Enable gui effects'; Apply 3. Uncheck it again; Apply
Not sure if this is a style bug. Applications can use QTreeView::setAnimated(), but I have not checked where the default comes from.
This should have been fixed with commit 41c24a337.