Comment # 5 on bug 1188074 from B

Same story here, the option under "Settings" doesn't exist.

Though if you right-click next to the menu bar a menu with checkboxes for "Main
Toolbar" and "Session Bar" appears. Unselecting them only removes the toolbars
for that sessions, reopening Konsole will bring back those toolbars.

Also, if I modify the toolbars, for example change their orientation to the
left and set them to Icon-only, those modifications don't persist.

Since we can reliably remove those toolbars by modifying the config files in
~/.local/share/kxmlgui5/konsole/ it seems to me that there's a bug that
prevents the config files from being updated when changes are made to the
toolbars. Other non-toolbar changes seem to persist fine.