The easiest way to install the default downloader is to select "Symbol -> Auto Manage Symbols". Check the exchanges you want to track, click on "Save". This will add new symbols and install new downloaders.
Note that the Yahoo, Alphavantage and many other downloaders are working.
For the Alphavantage downloaders, please check here:
https://www.quantshare.com/index.php?option=Tabs&tabIndex=5&type=Items&order=creation_date&keywords=alphavantage
You need to install the downloaders and run them from "Download -> Download Manager".
Finally, please tell me what exactly you mean by "strategy decay" and "custom charts"?
Trading financial instruments, including foreign exchange on margin, carries a high level of risk and is not suitable for all investors. The high degree of leverage can work against you as well as for you. Before deciding to invest in financial instruments or foreign exchange you should carefully consider your investment objectives, level of experience, and risk appetite. The possibility exists that you could sustain a loss of some or all of your initial investment and therefore you should not invest money that you cannot afford to lose. You should be aware of all the risks associated with trading and seek advice from an independent financial advisor if you have any doubts.