it's a good idea to start by getting familiar with the Intellij API, maybe getting a little plugin project running from scratch and looking through example code from other plugins such as intellij-rust and https://github.com/JetBrains/intellij-community/tree/master/plugins
I've found that as a general rule there is no such thing as quick and easy when trying to get a new feature working within intellij. I've put in hours of work into local branches that ended up going nowhere.
do you have any experience with BNF grammar / JFlex?