Cache contents of a popup menu to speed up search times.

Actually it was super quick for me to do, so here you go:

sf.ui.proTools.appActivateMainWindow();

function getFirstFreeInsertIndex() {
    var btns = sf.ui.proTools.selectedTrack.invalidate().insertButtons;
    let insertArray = [2, 3, 4, 5, 6, 7, 8, 9, 1, 0];
    for (let i = 0; i < insertArray.length; i++)
        if (btns[insertArray[i]].value.invalidate().value === "unassigned") return (insertArray[i]);

    throw 0;
}

function addNewInsert() {

    var numberOfPanSliders = sf.ui.proTools.selectedTrack.groups.whoseTitle.is('Audio IO').first.sliders.whoseTitle.startsWith('Audio Pan indicator').count;

    var insertBtn = sf.ui.proTools.selectedTrack.insertSelectorButtons[getFirstFreeInsertIndex()];

    var cacheKey = 'cachedInsertMenuItems_' + numberOfPanSliders;
    var menuItems = globalState[cacheKey];
    if (!menuItems) {
        menuItems = insertBtn.popupMenuFetchAllItems().menuItems;
        globalState[cacheKey] = menuItems;
    }

    var selectedPath = sf.interaction.popupSearch({
        items: menuItems.map(mi => ({ name: mi.path.join(' -> '), path: mi.path })),
    }).item.path;

    insertBtn.popupMenuSelect({
        menuPath: selectedPath
    });
}

addNewInsert();