I needed something like this today - was going to download Insomnia but I happened to check HN.

I tried it out; it's exactly what I wanted. Postman, as echoed in previous comments, has gotten out of control with the upsell and the confusing UI.

I bought the pre-order, seems like a good deal at $9, that's nearly the cost of a latte around here and if this works out I'll get a lot more use out of it than a latte.