On Linux and on other operating systems using X-Window for their graphical user interfaces, after you have selected some text, for example by dragging your mouse over it, you can paste it elsewhere by just clicking mouse button #2 (also called middle button or mouse wheel). That is, no need to use Copy (Ctrl-C) / Paste (Ctrl-V) to paste the selected text. On any X-Window system, this feature, called the system selection, is native and works across applications.
This feature is so handy that XMLmind XML Editor implements it, not only on X-Window systems, but also on Windows and on the Mac. However, on Windows and on the Mac, this feature only works within XMLmind's document views.
Note that unlike EditCopy (Ctrl-C) which copies characters as well as XML nodes, selecting text this way just copies characters to the system selection. For example, using this feature you can easily copy the content of an XHTML p element in order to paste it in a DocBook para element. (Using Ctrl-C to copy the content of an XHTML p and then using Ctrl-V to paste it in a DocBook para will not work if the p element has child elements.)