I know that you can remove duplicate lines by doing Edit>Permute Lines>Unique. But that will remove blank(empty) lines. I would like not to remove them, so blank lines will stay(essentially empty space).

CodePudding user response：

You can do this using Permute Selections. First, open the Find menu (CtrlF or Find → Find…) and make sure the Regex, Wrap, and Highlight matches buttons are selected. In the search field, enter ^. \n. This matches the beginning of the line ^, 1 or more characters of any type . , and the newline character(s). Therefore, it will select any line that is NOT just a newline. Note that this will select lines that contain only whitespace, for example a tab character followed by a newline.

Next, hit the Find All button to select each line individually.

Finally, select Edit → Permute Selections → Unique and all duplicate lines will be erased, leaving all blank lines behind.