The editor seems only to allow one space between sentences, made by pressing the space bar on your keyboard. Using the spacebar to put more than one space shows the spaces in the editor, but your final post won't show more than one.
I suppose if you wanted more than one space separation, you could just add more periods after the sentence..... Should work ok.
If you want an extra space between lines, Just hit the enter key 2 times after typing your sentence or paragraph.
That should do the trick.
If I want more than one blank line after a sentence or post,
I just put a period on each line.
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Then click the Preview Post button to check that it worked.