Here's the deal. In order for lookup to work, MT has to have a list of all available symbols/names/exchanges to display it.
Some sources supply this list. Right now it QuoteMedia and DXFeed (no, DXFeed has not been released yet). I am working on trying to get the information from IQFeed as well. Other sources, like Webull, TD Ameritrade, IB, etc. - we have no way of getting such list of securities from them. If we did we could easily add them to the lookup machinery.
So yes, lookup exists in MT but only if you utilize a source that supplies the full list of its available symbols to us, and there are very few such sources at the moment.