How do I open the application launcher ("start menu") of Kubuntu with my Windows key? Similar to how the Start menu in Windows is opened. I don't want to use Alt+F1.

How do I open the application launcher ("start menu") of Kubuntu with my Windows key? Similar to how the Start menu in Windows is opened. I don't want to use Alt+F1.

If you assign the launcher shortcut key to Meta+F1 or Alt+F1, KDE will instead interpret this as assigning it to solely the Meta key.
To open the settings window, right-click on the launcher icon and choose Configure Application Launcher. Then click on Keyboard shortcuts (as shown below).
After clicking Apply, the launcher should open when just pressing Meta. This currently works on Plasma 5.24 and 5.25.
Modifier keys like Ctrl, Alt and also the Meta (also called "Super" or "Windows" key, are meant to operate only as modifier keys. This design works its way down to the roots of all the libraries under the GUI you see using KDE: Qt, Xorg, etc.
Your exact question is here on the KDE Forums by the way: Super key to load Application Menu.
It seems however, that there's a large audience for this feature. So, in case you really want this to work, you could try the ksuperkey package, which contains all you need:
ksuperkey allows you to open the application launcher in KDE Plasma < 5.8 using the Super key (also known as the "Windows key"). If you hold down the Super key it will still act as a modifier key, allowing you to use it for other keyboard shortcuts.
ksuperkey is a small application that runs in the background as a daemon. It was forked from xcape by Albin Olsson: https://github.com/alols/xcape
ksuperkey can be installed from this PPA.
Note that KDE Plasma 5.8 and above will support this feature by default.
It doesn't do exactly what you are asking for, but ALT-Space opens a search box with which you can launch basically the stuff you could select from the Application Launcher.
Feature has been added by default since Plasma 5.8. If it's not working, make sure your "Start Menu" widget has a global shortcut like Alt+F1 set. You can't assign it directly to Meta, but it will open with Meta if another shortcut is assigned).
Right Click the KDE Icon → Application Menu Settings
Keyboard Shortcuts Tab → Shortcut: Alt+F1
Latte Dock:
If you're using Latte Dock, you will need to run the following commands mentioned in it's Wiki.
kwriteconfig5 --file ~/.config/kwinrc --group ModifierOnlyShortcuts --key Meta "org.kde.lattedock,/Latte,org.kde.LatteDock,activateLauncherMenu"
qdbus org.kde.KWin /KWin reconfigure
https://userbase.kde.org/Plasma/Tips#open-start-menu-with-windows-meta-key
simple workaround without loosing meta: meta + z (u.s. layout)
can be hit with just one finger at one
I'm on Plasma 5.8.5 and I can enable this feature by going to System Settings -> Input Devices -> Keyboard -> Advanced -> The third checkbox should be "Alt/Win key behavior" -> Choose "Meta is mapped to Win keys" -> Apply
You are all set :)
kwriteconfig5 --file ~/.config/kwinrc --group ModifierOnlyShortcuts --key Meta "org.kde.plasmashell,/PlasmaShell,org.kde.PlasmaShell,activateLauncherMenu"
works most of the time for me. It adds the setting to the kwin config file. This means it defines a new so called "ModifierOnlyShortcurt", which is just the Meta key to activate the launcher menu.
While the accepted answer may have worked a few years ago, ksuperkey does not seem to work on Kubuntu 15.10, when installed from PPA. I have no doubt ksuperkey is a better solution, but I ended up following the link in gertvdjik's answer and using this solution, which works absolutely fine. Posting here for future googlers who had the same trouble as I did.
For brevity;
NOTICE: YOU WILL LOSE THE META KEY - so you might want to map it somewhere else.
Run
xev | grep keycodepress the meta key and watch the output (the code is likely 115)then add an entry to your Xmodmap configuration:
echo 'keycode 115 = F13' > ~/.Xmodmap"xmodmap ~/.Xmodmap" will change the keysym to F13 (not present on most keyboards ;-) and you can use it like any regular key.
If your distro does (probably) not invoke ~/.Xmodmap by default, add a short script to
~/.kde/share/autostart/xmodmap.shxmodmap.sh: #!/bin/sh xmodmap $HOME/.Xmodmapand make it executable
chmod +x ~/.kde/share/autostart/xmodmap.sh
For me, the keyboard shortcut Windows + Enter worked (Kubuntu: 22.04/KDE Plasma: 5.24.6).
Application Launcher icon, select Configure Application Launcher.Keyboard Shortcuts tab and click on Input ... button.(Windows = Meta = Super = same key.
Enter = Return = same key)
Ok to save the configuration and test.Things have changed in Plasma 6.1 concerning "modifier-only" shortcuts: they can be configured visually with the Shortcut system settings and are now stored together with other shortcuts in “~/.config/kglobalshortcutsrc”.
https://www.lorenzobettini.it/2024/06/modifier-only-shortcuts-in-kde-plasma-6-1/
I have also be confused about this question weeks ago.
Today I added a panel and a Tiled Menu on it. Then I use alt+F5 to activate it.
Beacuse alt+F1 F2 F3 F4 are alreadly occupied. Really, not alt+F1.
It happened just after reboot that the Super was back to life!
So I think that:
The one on Latte Dock won't work.
The one on a default panel will do.
It's interesting.
KDE Plasma Version:5.14.5
KDE Frameworks Version:5.54.0
Debian 10.3
It just randomly stopped working today for me. Had to right click the Application Launcher (start menu) > Configure > Assign a new keyboard shortcut 'Meta + Z' because some ditzy person decided to disable the option to just use Meta (That I can assure you was deliberate) Then. Boom! It started working with just Meta and also Meta + Z.
What a silly solution all because KDE has dementia and can't remember what happened 5 minutes ago. History in Konsole, Screen layouts, etc etc. There are many such examples.