Link (include? import?) one script to the other - templates, presets and require / module.exports

Maybe your are trying to change the variable on the other script.

For that you would use globalState to save a variable that you can use globally in SF.

function returnCategory() {
    return globalState.whaddup;
}

module.exports.returnCategory = returnCategory;

and to call:

const { returnCategory } = require('package:ckunujin000022l10mtpbk86y');

globalState.whaddup = 'hi there'
log(returnCategory());

I'm not sure it makes sense in this case.
You can pass the variable on the function properties.
For example:

function returnCategory(whaddup1, whaddup2) {
    /*     var logic = sf.ui.app("com.apple.logic10");
        var trackArea = logic.mainWindow.groups.whoseDescription.is('Tracks').first.groups.whoseDescription.is('Tracks');
        var trackHeaders = trackArea.allItems[1].splitGroups.first.splitGroups.allItems[1].scrollAreas.first.groups.whoseDescription.is('Tracks header').first;
        var selectedTrackName = trackHeaders.getElements('AXSelectedChildren').first.getString("AXDescription").match(/“(.*)”/)[1] */
    let trackName = "lv"
    switch (true) {
        // TRACK
        // lv
        case trackName.includes('lv') || (trackName.includes('lead') && (trackName.includes('vocal') || trackName.includes('vox'))):
            return whaddup1;
            break
        // bv
        case (trackName.includes('harm') || trackName.includes('group') || trackName.includes('chant') || trackName.includes('gang') || trackName.includes('bv')) || (trackName.includes('back') && (trackName.includes('vocal') || trackName.includes('vox'))):
            return whaddup2;
            break

    }
}
module.exports.returnCategory = returnCategory;

and to call:

const { returnCategory } = require('package:ckunujin000022l10mtpbk86y');

const whaddup1 = 'hi there'
const whaddup2 = "another hi"

log(returnCategory(whaddup1, whaddup2));