MacOS – Bind a CTRL key to custom button

I think this is a bug in Mac OS X and has something to do with the way the keyboard shortcuts for Spaces are processed. Try this:

• Make sure Spaces is turned on in the System Preferences with the standard 4 spaces layout, and standard key combination for switching to a space.
• Open a folder in the Finder.
• Press and hold CTRL, and press any of the number keys. If you press 5, 6, 7, 8, 9 or 0 first you will get a beep. Same if you press one of those keys again (still holding CTRL). If you then press 1, 2, 3 or 4, you will switch to that space number; or just stay in that space if you were already in it. If you then press any of 5, 6, 7, 8, 9 or 0 again, it won't beep anymore.

If you simply turn off Spaces, the above won't happen and whatever order you press the keys in, they will continue to beep. If you change the number of spaces to only two, then 3, 4, 5, 6, 7, 8, 9 and 0 will give you a beep until you've pressed either 1 or 2. I don't know of an application in which those keys have a non-Spaces functionality and would do something useful other than beep, so I haven't been able to try what happens in such an application. In any case, I don't think you need to worry there's something wrong with your keyboard or the way you've configured the keyboard bindings; it seems to be a bug in Mac OS X.

Edit: Try the above in a new folder in which you've created folders named "1", "2" and so on. I find the Finder's behavior in this case somewhat strange: if you press CTRL-8, it will beep yet also switch the selection to the folder named "8". But again, pressing 5 through 9 will neither beep, nor change the selected folder once you've pressed any of 1 through 4.

Got this all from more recent Brett Terpstra posts, so full credit to him.

Using Karabiner Elements and BetterTouchTool, you can create a "Hyper" key mapped to control-option-shift-command (which probably won't be used by any apps as a default modifier). Then you can use BetterTouchTool to maps Cap Locks + "a" to type "=". Typing "a" by itself still gets the letter "a". You can also set it up that tapping Cap Locks alone functions as the escape key or even as standard Caps Lock.

Rather than reposting Brett's code here, I'll link to the post: A Hyper Key with Karabiner Elements, full instructions.

Some screenshots to help guide you along:

After adding Brett's code to karabiner.json, the Complex Modifications pane will look like so. No need to do anything else here.

In BetterTouchTool, switch to the Keyboard pane, add a shortcut, type Caps Lock + character, then choose "Insert/Type/Paste Custom Text" as the Trigger Predefined Action.

In the Insert/Type/Paste Custom Text sheet, type the character(s) you want and choose "Insert Text by Typing".