"I'm trying to use eg. "*" when using Search and Replace but it doesn't work."
Short answer: "It doesn't work" is Correct.
Find and replace in Numbers searches for the specific string of characters entered in the Find box and replaces that specific string with whatever you've placed in the Replace box. It does not offer the option of limiting the finds to "whole words" nor does it offer the option of using the wild cards * or ? (or ~).
From the linked article (emphasis added):
"The string operator (&) can be used in formulas, and wildcards (*,?,~) can be used in conditions."
(note there is no mention of use in the Find and Replace dialogue.)
"conditions" are required arguments in the ...IF and ...IFS functions.
An internet search using "search" as a keyword will include this article in its results because the discussion includes the SEARCH( ) function as one which requires the ~ operator to treat the wildcard characters * and ? as literals rather than wildcards.
Regards,
Barry