I think I have found a method.
Under the drop down menu Line and Paragraph spacing is the option Remove space after paragraph. That seem to work and using that when I want the usual (double space) after the end of a paragraph I just need to press Enter twice.
And now when I want normal line spacing when the lines dont extend to the end of the line I just press Enter once and then I don't have the problem of the tab key indenting all the lines when I press Shift Enter.
It might appear very clumsy and cumbersome but the documents I am creating usually are only 2 or 3 pages in length.
Maybe there is a better method ?