jEdit's register feature is a powerful extension of the clipboard metaphor. From the Edit - More Clipboard submenu, you can see the cut/copy/append/paste register actions. C+r C+c X copies the selected text to register X. C+r C+v X inserts the contents of register X into the buffer. Register contents are persistent between editing sessions.

You can see the contents of all registers in a dockable by invoking View Registers.