Display hotkey presses Mac OS X

KeyCastr seems like it does what you want.

From the Readme:

KeyCastr, an open-source keystroke visualizer

I’ve made an app for that too. Take a look at Keystroke Pro!

Preview video: https://youtu.be/3koqaw99uKA (30 sec)

Download: https://ixeau.com/apps/keystroke-pro/

How to install it:

1. Download the app: Link.
2. Unpack the keystroke-pro.zip archive you’ve just downloaded.
3. Drag the unpacked app to your applications directory.
4. Start the “Keystroke Pro” app.

How to use it:

• In order to detect keypresses the app needs to be added to the macOS Accessibility tab: System Preferences... > Security & Privacy > Accessibility
• You’re all set now. The app lives in your macOS status bar—you can activate it from there. Take a look at the preview video for further impressions.