Make sure to create devicetree files before you use the editor.
The Devicetree Visual Editor is meant to be used with existing .dts, .dtsi, and .overlay files. For this reason, it does not offer the option to create these files from scratch.
Important
In most cases, you should use .overlay files, and use them for application-specific changes. The only exception is when working on a custom board. When working on such boards, you can work on .dts and .dtsi files, but make sure to manipulate only your board's files. Directly editing .dts, .dtsi, or .overlay files that come with an SDK installation may have unintended consequences to other boards or to applications that use the same board.