The levenshtein operator is certainly a potential aid… But I also think that it won’t be entirely sufficient for what you want.
Suppose you already have, say, a very short and a very long version of the same basic tiddler content. The very short tiddler will still “match” (according to levenshtein) every other very short (unrelated) tiddler “better” than it will match the long one that just has more details on the same theme.
(Perhaps there’s a way of combining levenshtein distance with length comparison, so that internally duplicated strings become more salient… )
I’d encourage trying freelinks from the official plugin library (or turning them on for occasional surveying/maintenance work) as another tool, and perhaps taking advantage of an alias plugin.
If you make sure to develop the habit of specifying aliases for your tiddlers (and especially if even those aliases automatically show up as links), you’re less likely to repeat yourself by creating a near-duplicate tiddler using slightly different words.
I also make use of “see-also” fields in some projects, to help me browse through related tiddlers even when tags and internal tiddler links are not the best tool for connecting things.