Great application; here are a few suggestions

Thank you for writing this application! It works great!

I have a few suggestions that may make this application even better.

Currently you have a bar just for the full url. As others have stated, this is a problem because some urls are very long when we are using certain types of APIs.

A great solution would be a url-builder UI, which allows the user to construct the URI easily.

Secondly, the user interface can definitely be improved.

Although the user interface gives freedom for the components sizes, the lack of organization makes it less aestheticly pleasing, and less easy to use.

For example, the header data table is great, one thing you could do is make it editable in the table itself.

Using some of Lions built-in views may make this app a complete, 5-star application.

Thank you for your great work! I look forward to seeing updates soon!

skaushik92 about GraphicalHttpClient