As I have also been frustrated with the direction Postman has taken, I have a great alternative to suggest, if the only thing you want to do is fire requests on demand easily and do not need automated testing.
The VS Code Rest Client extension https://marketplace.visualstudio.com/items?itemName=humao.re... is great for testing and debugging APIs.
You create a "my_request.http" file that contains something like
POST https://example.com/comments HTTP/1.1
content-type: application/json
{
"name": "sample",
"time": "Wed, 21 Oct 2015 18:27:50 GMT"
}
First line is the method and url, then headers, then a newline, then the request body.
Hit ctrl+alt+p, the request is sent and you see the response in a side pane. Everything is encoded and decoded properly.
You can organize your tests under multiple files and folders.
I cannot recommend this extension enough, it has made my life so much easier.