Here's an alternative I recently came across. In Firefox on the network tab of the dev console, right click on an XHR request. You'll have two relevant options: "Resend" and "Edit and Resend". Edit and Resend doesn't give you all the features of Postman, but it is useful and a lot easier. I have spent a lot of time in Postman just putting in all the headers and POST body to set up the API call. With this method in Firefox, all parameters are already set because it's an exact copy of the request you already sent. You can change params or just hit send when you're ready to retest something you're doing on the backend.
I am very happy to save you a lot of time for copy&pasting requests to Postman. Since Postman can import curl commands, just right-click on a command in Firefox, Copy as -> Curl, click on the Import in Postman, import as text, paste curl, mission accomplished. Hope it helps.
