As if they don’t know about this. This has probably been suggested to them thousands of times over the years and they ignored it.
It is Edit > Find and Replace Ctrl+H. It is not necessary to replace anything, use Find Next, Find Previous, or Find All
On believe me I tried.
By the way, in MS Excel (at least until Excel 2019) there is no such possibility. And regular expression search in UI is not supported.
… and the very first time ever, when this proposal was made “over the years”, was tdf#127174 in 2019, which was confirmed, and the UX decision was “let’s do it”. And there was not a single duplicate neither before, or after, showing how important this feature is for users who use Calc properly.