LO Help has no informations about Search field in special character dialog: https://help.libreoffice.org/7.1/en-GB/text/shared/01/04100000.html?System=WIN&DbPAR=WRITER&HID=cui/ui/specialcharacters/help#bm_id3146903 For example, it wasn't clear to me, that it is possible to enter the word "Tilde" and all characters with a tilde are displayed.
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/5c2a52e32028e4d894704f171b18937786866686 tdf#138193 SPECIAL CHARACTER DIALOG: Help for search field is missing
Verified with https://help.libreoffice.org/7.2/en-GB/text/shared/01/04100000.html?System=WIN&DbPAR=WRITER&HID=cui/ui/specialcharacters/help#bm_id3146903 Olivier, thanks for fixing it!