I search for
(spacebar)(spacebar)+ in Regex
You could also use
(spacebar){2,} ( (spacebar) means tap the space bar, don't type the word in!

)
Either way means you are looking for two or more spaces.
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Another Regex that I use all the time (usually just before the one above) is
Search:
\n
replace:
(spacebar)
That removes ALL line feeds & replaces them with spaces.
After I've done the two operations above, I Beautify all files, which puts in only the necessary line feeds.