Sideberry extension gives you a lot of what you're looking for. You can have separate tab panels for each container, and a keybinding (ctrl+space by default iirc) that opens a new tab in the current panel and the current container.
The capability to convert a network request from one format to another is the main reason I use Postman, which has a great implementation of this and a ton of tools and languages it can do it in. This looks great as well
Much love for Rockbox. I used to run this on the iriver h120 and use it for amazing lossless recording on the cheap. This was one of the earliest things that got me interested in open source.