Features in KDE-PIM
Gui: Window: Sync Navigation and Show Toolbar checkboxes and save window state
Navigation checkbox (right click on toolbar) doing same as Show Toolbar
checkbox (View menu). Synchronize state of both checkboxes, so user will see
always correct state of both checkboxes.
State of main toolbar (visible or invisible) is stored in trojita config file
in gui/sizeInMainWin by saveSizesAndState (e.g when changing main window layout).
So call method saveSizesAndState() when state of main toolbar is changed too.