I see that https://auspice.us/ has drag-n-drop feature to drop user files (for example, json files). But I don’t see that similar feature at auspice app (github.com/nextstrain/auspice). How can I put similar drag-n-drop feature in auspice app ?
The main auspice app has drag-and-drop functionality for metadata, as documented here. auspice.us is a separate program, and it contains speicif code to customise the auspice client in order to use specific drag & drop logic, which allows users to drag & drop dataset JSON files to visualise.
If you are interested in customising auspice to suit your particular use case, there are docs here and the auspice.us source code is here.