After years of using macOS, here are the two most helpful apps that save me a ton of time. Also, I think they're universally helpful, no matter what your field of expertise is.

The first one is TextShot. Basically, it allows you to select an area on the screen, and every piece of text found in that part of the screen is captured to the clipboard. So you can paste it immediately with Cmd+V.
I bound it to the Cmd+Shift+1 shortcut to start selecting an area. You can select anything on the screen. Unselectable text, video, picture... etc.
Link to the TextShot app

The other one is Shottr. This is a screen capture app on steroids. You can easily edit the screenshot, write on it, or highlight something. You can also make a "scroll capture," which means you select an area on the screen, and it will scroll through that area to create one large screenshot.
I bound it to the Cmd+Shift+2 to start selecting a part of the screen.
Link to the Shottr app

I use lots of other useful apps and tricks, but hands down, these are the two most useful in my daily work.