Eclipse Neon provides a WTP Eclipse JSON Editor which can be extended with JSON Schema to provide custom completion.

If you have install JSON Editors with Eclipse Neon

you will have an editor for tsconfig.json

TSConfig editor provides several pages to manage tsconfig.json options with UI:

• Overview page

The compiler section gives you the capability to see and choose your TypeScript version and nodejs executable:

• Files page

• Output page

• Source page

Here a sample with completion for tsconfig.json: