Use SEND function, withdraw is still in development. And yes, you can send to any external BTC address, just use SEND button.

I think withdraw would be an option to cash out or similar, for transferring BTC you use SEND.

Go Waves! This is big news guys!

https://blog.wavesplatform.com/deloitte-cis-and-waves-platform-to-shape-the-future-of-blockchain-674e17c3b067

Deloitte CIS and Waves Platform, a leading developer of blockchain solutions, signed a memorandum on strategic partnership.
The partnership is aimed at providing clients with comprehensive initial coin offering (ICO) services and customized blockchain solutions tailored for specific business tasks.

Deloitte is one of the "Big Four" accounting firms and the largest professional services network in the world by revenue and number of professionals.Deloitte provides audit, tax, consulting, enterprise risk and financial advisory services with more than 244,400 professionals globally.In FY 2016, the company earned a record $36.8 billion USD in revenues. As of 2016, Deloitte is the 6th-largest privately owned organization in the United States.