USB OTG support demoed on Windows 10 for Phones
USB Flash Drive support, UI changes, demonstrated on video
Microsoft is working on a number of new features for Windows 10 Mobile. In addition to Continuum, which is a technology for converting a phone into a PC, the next generation of Windows Phones will support USB Flash Drives. Some of the older Lumia models will also benefit from adding USB OTG support to Windows 10.
USB On-The-Go (USB OTG) will allow you to connect a flash drive to your phone and extend the internal storage at any time. Microsoft has confirmed at BUILD 2015 that future Windows 10 phones will come with USB Dual-role hardware support, just like the working prototype seen on the video bellow:
Along with USB support, you can also see some UI changes in the mobile OS like 4 mid-side tiles on the start screen and ‘app apps’ before the arrow at the bottom of the screen. Another previously unseen feature is the redesigned Explorer app with a split view menu and white background.
Source: Nokia Power User