We have Ctrl+Shift+M to close main bar but I can't find option to close that split menu thing. It steals two lines of text. This should be optional. If you are unwilling to use proper shortcuts, enable it in Settings and use mouse whatever.
It's toggled through the menu: Settings > Toolbars Shown > Main Toolbar. It would be helpful if this was also in the main settings dialog.
Fixed in Konsole Version 21.08.1 Great! ;)