Example: The following text:

Hello,

How are
you this
evening?

will be transformed into:

Hello,

How are you this evening?

This plugin actually applies successively two regex:
Search = " +\n"
Replace by = "\n"
to remove spaces at end of lines (and lines composed only of spaces), and then
Search = "(?<=.)\n(?=.)"
Replace by = " "
to replace all the \n inside a paragraph by a single space.

The operation will be done on the selected text, if any, or on the whole text if there is no selection.