Kubuntu - Dolphin panel - hide "Recently Saved" and "Search For"
Places
Dolphin handbook
Dolphin > Help > Dolphin Handbook (F1)
or
online: https://docs.kde.org/stable5/en/applications/dolphin/index.html
Places
A right mouse button click opens the context menu to edit, add, hide or remove entries and change the icon size to one of the predefined values or lock/unlock the panels.
Right clicking - hiding and unhiding:
Future ?
Bug 300247 - Allow hiding individual groups in new Places Panel: https://bugs.kde.org/show_bug.cgi?id=300247
Under review - Hidding Group from KFilePlacesModel: https://phabricator.kde.org/D8367