While
Mumu looks like a great little app and even trying it it's way faster than what macOS ships with, I feel that paying 20$ or even 12$ right now is waaaay too much for an app like this (for 1 device, for 1 year).
- You already have an emoji picker for free
- Rocket Pro costs 5$
- You could use the native text replacements on macOS or even Alfred, TextExpander, Keyboard Maestro, aText, Rocket Typist etc. and recreate this. You don't even have to do it manually as you'll find a couple of open source projects already created that list for you (https://github.com/warpling/Macmoji)