Functionally DEX is great, but drawbacks are the lack of speed and experiencing extensive lag. You have to enter waah in the search bar, but dont do it too quickly. After opening the wallet and going to DEX, wait a good few seconds for the default WAV/BTC pair and its order book to appear. Only then search for waah. It should appear. If it doesnt then you searched too quickly and you have to close and re-open the wallet.