MarkText does it - even if you don’t know regex. I use markdown almost exclusively, so also tried Typora and Obsidian - niether of which are FOSS and both have excellent search abilities just like MarkText. Marktext can sometimes be buggy - at least the later versions have been.

Try Catfish, too - but you need the exact file name usually.

Here is my cheatcheat list for when my old brain doesn’t recall the directory or details: locate TODAY.md locate <filename>

locate -i <file name> even without the extension. ♥️ this one may be the best!!! takes one second to find, but you must know the entire file name first, though not the extension. If you only have one of the words in the file name, it brings up the relevant list. the -i is for ignore case.

find ~ -ipath ‘*journals’ {find directories ending with whatever is after *}

find ~ -name this_week.md -exec micro ‘{}’ ; find ~ -name <filename> -exec micro ‘{}’ ; {you need to either use micro or substitute in the name of your editor, such as nano or vi maybe. it finds the file, then opens it in your default editor}

fdfind ‘MY*.md’ -g fdfind ‘*week.md’ -g {i think i had to install this one. the others above came with Debian}

I researched this subject 2 days ago and am still working on it. I love Marktext, but it is a big window and a heavy program to have to open when a terminal will do.