Select Duplicate from the Block menu to insert a copy of the selected text at the current position of the text cursor. The newly inserted copy will become the selected text.
This command is intended to be used with persistent selections. You can move the text cursor without clearing the selection only when selections are persistent.
Selecting text, moving the text cursor, and invoking Block|Duplicate has the same effect as selecting text, invoking Edit|Copy, moving the text cursor, and invoking Edit|Paste. The only difference is that Block|Duplicate does not use the clipboard, so the contents of the clipboard are preserved.
The option "paste whole lines when lines are copied as a whole" affects how text is duplicated when you have selected complete lines. Selecting a complete line means to select everything from the start of the line to the end of the line, including the line break at the end of the line. Selecting multiple lines completely means selecting everything from the start of the first line in the block until the end of the last line in the block, including the line break at the end of the last line. When the option "paste whole lines when lines are copied as a whole" is on, whole lines are always duplicated as if the cursor were at the start of the line when you invoke Block|Duplicate. Thus, whole lines are always duplicated as a whole before the line that the cursor is on when duplicating. This makes it easy to duplicate blocks of lines without worrying about the horizontal position of the text cursor. If this option is off, the selected lines are duplicated at the exact spot the text cursor is at, even when whole lines are selected.
If you use the menu item or toolbar button to invoke this command, it will be invoked on EditPad's main editor, where you edit files. If you press the shortcut key on the keyboard, it will be invoked on whichever editor is showing the text cursor (vertical blinking bar), whether that's the main editor, the search box or the replace box.