OK, I had no idea this was so easy (and so hard to remember). I'm glad the days of function keys are over because remembering these is impossible but from Apple, here's how to do screen grabs without having to start the screen Grab app:
- Shift-Command-3 will grab the entire screen. You will hear a click when it does it.
- Shift-Command-4 will turn the cursor into a cross hair and drag-select to get a portion
- Shift-Command-4 and hitting Space will highlight a window that you can grab
- There there are some useless ones, Shift-Command-6 takes a capture of your Touchbar and
- Command-<comma>. Doing a Command with the comma key opens up the preferences for the current application.
- Command-Option. This clears away all the windows that are in front of the window you are looking for. Useful if you don't use things like Divvy to prevent overlapping windows.
- Command-L. this gets you into the search bar of the browser and highlights the entire URL for you