Basically, no, imo. A fiction writer should just know all those words and use the right word in the right sentence.
However, James Scott Bell has this take on the question, over at Kill Zone Blog.
Now, of course, we all have personal computers with a Dictionary/Thesaurus app. I use mine most often to find a synonym for something mundane, like walk. Sure, a character can walk into a room. That doesn’t do much for the reader. So I open my computer thesaurus and in five seconds find: stroll, saunter, amble, trudge, plod, dawdle, hike, tramp, tromp, slog, stomp, trek, march, stride, sashay, glide, troop, limp, stumble, and lurch.
And that is all very well, but you had better know the difference between a saunter and a sashay or you are going to mess up your scene.
Also — and I’m sure this isn’t an issue for Bell — but one of the hallmarks of amateur writing is the overuse of words like march and stride and sashay and so on when the character should, in all honesty, just be walking.
However! Having glared at the post and muttered Bah, humbug! under my breath, I will say, the synonym button in Word is actually sometimes useful. Not so much for finding synonyms for “walk,” but for getting to a word that is on the tip of your tongue, but you can’t quite pull it up.
In that situation, you can type a word you know is not quite right, click on “synonyms,” pick a word that is still not right but closer, repeat a couple of times, and bingo! THERE is the word you were trying to recall that whole time.
So for me, the synonym button is helpful to jog my memory when the vocabulary part of my brain freezes up, rather than particularly useful in avoiding redundancy in word choices.
While we’re on the subject, “look,” is a place where synonyms both are and are not helpful. The problem here is that “look,” like “said,” is largely invisible, but that can easily lead to overusing the word.
She looked at him or He looked surprised are the sort of phrases that get used over and over. That’s hard to avoid. It’s true that you can try to describe a surprised person — his eyes widened and so on — but quite a bit o the time, it’s simpler and quicker to say He looked surprised and then move on briskly, without giving the reader time to dwell on that sentence.
But let’s pull up a synonym generator and take a look. Okay, here are synonyms for “look” as a verb:
glance, gaze, stare, gape, peer, fix one’s gaze, focus, peep, peek, take a look, watch, examine, study, inspect, scan, scrutinize, survey, check, contemplate, consider, see, observe, view, regard, pay attention to, take note of, mark, check out, glimpse, behold, spot, spy, lay one’s eyes on, catch sight of, eye, take in, ogle
A small number of those words are also basically invisible. “Glance” and “gaze” are both good if you don’t want to draw the reader’s attention. They also aren’t synonyms: a glance is fleeting and a glaze longer, which is why the writer ought to know both words and not mistake one for the other.
Many of these so-called synonyms do mean something other than “look” and/or do call attention to themselves. Saying, “She gaped at him” is completely different from “She looked at him.” Gape is never invisible; it’s the sort of word that always draws attention to itself and always creates a specific sort of visual impression, provided the reader is the kind of reader who visualizes the scene. I don’t think I have ever in my life used “gape.” I do visualize scenes and I don’t like the visual effect of this word.
Saying, “She contemplated him for a long moment,” is different in another way. Saying, “She paused for a long moment of contemplation,” or something like that, and now we are into a strikingly different style.
One more note on this topic:
Bell says: I was writing a scene with a drug kingpin and his pet monkey. The monkey keeps shrieking. But I didn’t want to use that same word over and over. So I popped open the thesaurus and immediately found: scream, screech, squeal, squawk, roar, howl, shout, yelp. Just what I needed. I used five of them.
And my instant reaction was: five, really? Because I only see three words in that list that seem suitable for, say, a Capuchin monkey. (Just a reasonable guess about the most likely kind of monkey.) Capuchins don’t roar, howl or shout, and I’m not crazy about squawk or yelp either.
By the way, speaking of roaring monkeys, when I was in Venezuela listening to howler monkeys, I once spent some time trying to come up with ways to describe the sound they make. The best I could do was “Like a cross between lions roaring and power saws, cranked up to eleven.” That is not a sound I know how to capture in one word.