I understand that "with/in your web browser" implies a extention or simmilar, but i have good experience using Selenium and Python to scrape websites. Some sites are trickier than others, and when you are instrumenting a browser it easily triggers bot prevention, but you are also able to easily scrape pages that build the DOM using JS and simmilar. I have considered, but not looked into compiling my own Firefox to disable i.e. navigator.webdriver, but it feels a bit to much work.
This is my project for extracting my (your) webshop order & item data https://gitlab.com/Kagee/webshop-order-scraper