It is very easy to accidentally remove the Quicklaunch widget from the panel. That is a minor PITA, because to set up the Quicklaunch the way I like it takes 10 minutes. I have accidentally done this more times than I can count while trying to modify something in the Quicklaunch.  

As far as I know the only way to remove any other widgets from the panel is to go in to Panel Settings, and if you do remove the widget it immediately gives you an option to Undo your action. The Quicklaunch is the one widget which you can remove from the context menu with no confirmation or undo, and this is particularly egregious, since it is the one widget that actually takes more than a short time to set up properly.

SUMMARY

It is very easy to accidentally remove the Quicklaunch plasmoid from the Panel from the context menu and there is no way to undo this action.

STEPS TO REPRODUCE
1. Attempt to add an application shortcut or change a setting in the Quicklaunch. 
2. Accidentally select Remove This Quicklaunch.
3. Must go in to Widgets, and set up Quicklauch with my preferred settings (2 rows) and all my preferred applications.

OBSERVED RESULT


EXPECTED RESULT

There should at least be a confirmation dialogue box or an Undo option.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: 
KDE Plasma Version: 
KDE Frameworks Version: 
Qt Version: 

I have observed this behaviour in every version of Plasma 4 & Plasma 5 that I have used for the last 10 years. Mostly I use versions of Debian and Kubuntu.

ADDITIONAL INFORMATION

No other widget asks for confirmation before removal, so this would be inconsistent--and annoying, too. Instead, when you remove a widget, a notification pops up with an undo button that allows you to undo the removal. If you miss the notification, it's there in your notification system tray widget. So it's easy to recover if you accidentally remove it.