So I am writing a plugin for latex symbol completions, is there a way where once I type \phi it will then replace \phi with its respective symbol Ο and not just \phi? I know this blog Intro to Kakoune completions - Screwtape's Notepad exists but I am kinda stuck because I want it to replace the \phi with its symbol. Hoping for a kind reply 
EDIT: I apologize in advance as I am also new to kakoune scripting too 
Hi uncomfyhalomacro, and welcome to the community!
Have a look at tex-input.kak for some ideas. I tried like this kakoune-math.kak and let kakoune-snippet-collection or snippet.kak do the heavy lifting.
But if your like me all that will do is rob you of a learning opportunity when your just getting started. So, when I first started I lived here kakoune/rc/tools to build a good knoweledge base of kakounescript.
Hope this will help you on starting your kakoune journey and heres a beat to get you going.
Dizzee Rascall 2017, βThe Other Sideβ, Raskit, Spotify, viewed 13 April 2022, https://open.spotify.com/track/1JfIEk7aEkBnASi0dDoI0e?si=37c6e036537840ef
Hit the search bar for @Screwtapello his got some great stuff to get you started on the right foot. Bye 
Forgot, this is my solution to completers javaInheritanceHierarchy.kak