This is a place where we "must" behave like most systems. Dolphin does "not" have a selectable "Paste" action. Instead, it has "Paste from Clipboard". While this action is descriptive, users can be confused by the addition of Clipboard. In KDE the clipboard can have multiple items copied to it so it can become confusing for users to understand what will be pasted. "Paste" is more universally understood. Please implement it.
The action is actually generally named "Paste Clipboard Contents", not "Paste from Clipboard." There is only one place in Dolphin's codebase where I can find something named "Paste from Clipboard", and it's overriding the standard thing, which is "Paste Clipboard Contents". It probably should not. It looks like the "Paste Clipboard Contents" text comes from KIO, in KIO::pasteActionText(). It needs to be changed there. And this does look like this may be a bug, since the KStandardShortcut text is just "Paste". So there was an intention at some point for "Paste" to be the standard text.