I'm the creator of Insomnia and I'd love to hear your feedback if you try it out! I'm still a novice to GraphQL, so I'd like to make sure that it accommodates all use cases.
Cool. Insomnia is quite good. I prefer it over Paw (for MacOS only) because it is cross platform and I only want to learn one tool that works on both Mac and Linux.
Lots, actually. Since Insomnia is a full-featured HTTP testing tool, you can use all other Insomnia features with GraphQL like setting custom headers, filtering responses with JSONPath, Nunjucks templating, etc.
Purely aesthetics. I'm a weirdo, but a pretty UI really enhances my development experience. I'll use a less functional product if it pleases my pupils, like Hyper over iTerm2. (Not saying insomnia is less functional, it's just very pretty :)
You are probably correct. The server-side GQL implementations I have worked on expect only POST requests, and expect each requests' body to contain a query or a mutation.
~ Gregory