How to find undefined class methods in JS without hovering

Assume the following example:

export default class TestClass{
    constructor (){
        this.init();
        this.doOtherStuff();
        this.doMoreStuff();
    }
    init(){
        //do stuff
    }
}

This displays in VS Code as:

If I Ctrl+hover over the method calls, I can see that init is defined, while the other 2 are not.

I am looking for either an option to color differently the other 2 functions, or the reverse of the “Outline” panel.

“Outline” panel shows methods defined, I want to see methods which are called, but not defined.