Check this engine source code
bool SKismetInspector::IsPropertyVisible( const FPropertyAndParent& PropertyAndParent ) const
{
const FProperty& Property = PropertyAndParent.Property;
// If we are in 'instance preview' - hide anything marked 'disabled edit on instance'
if ((ECheckBoxState::Checked == PublicViewState) && Property.HasAnyPropertyFlags(CPF_DisableEditOnInstance))
{
return false;
}
In my opinion, it seems to display only the editable properties in the details panel during the instance editing mode.