How to work around the PT legacy menu not supporting Tab to search.

Use this script:

function getMenuAtMousePosition() {
    var mp = sf.mouse.getPosition().position;
    var element = sf.ui.root.getElementAtPosition(mp.x, mp.y);
    while (element.role == 'AXMenuItem') {
        element = element.getParentElement();
    }
    if (element.fullRole == 'AXMenu' || element.fullRole == 'AXWindow:AXDialog')
        return element;
    return null;
}

var menu = getMenuAtMousePosition();
if (menu) {
    menu.getMenuItem('search...').elementClick();
}
else sf.keyboard.press({ keys: 'tab' }); //Fall-through

And assign TAB to it in Pro Tools:

Note, this requires 2.2.0-preview.1.3 or newer