Most KDE Apps have an integrated HUD-interface / command bar called KCommandBar.
You can use it to list and search actions that are in the app’s menu using the shortcut Ctrl + Alt + i
details from @ngraham’s blog: “You can also use it as search, if you think a feature may exist somewhere but you don’t know where. Notice how it shows you the action’s keyboard shortcut too, so you can learn how to activate it even faster next time!”
Here’s a video of various things you can do with KCommandBar: