I'm not sure how hidden it is, but I'll mention MacVim - https://macvim-dev.github.io/macvim/. It's a great balance of an effective editor that integrates with a GUI. I love being able to copy/paste any amount of text between MacVim and other GUIs.
Outline tool Bike has great search implementation, exquisite outline item rearranging, and outline navigation.
Available at Hog Bay Software https://hogbaysoftware.com
I wouldn’t have any idea what I had coming up if it wasn’t for MeetingBar. Puts a nice item in my menubar telling me what my next appointment/call is, supports clicking to open the call and I can configure where it opens (Meet works better in Chrome, Teams opens the native app, etc).
https://github.com/leits/MeetingBar
https://apps.apple.com/us/app/id1532419400
Okay, let's start something new here!
1️⃣ Post about your favourite, somewhat obscure app or utility for #macOS. Can be 3rd party, can be built-in, both are fine! Tell us why you like it in a sentence or two.
2️⃣ Use the hashtag #HiddenGemsForMac.
3️⃣ Add a link and if possible, the Mastodon handle of its creator(s).
♻️ If you think that's a good idea, boost this here post so many people see it!
I'll keep an eye on the hashtag and boost your entries. Let's give some love to some indie #Mac devs!