(this is also a great way to figure out what you need to do for a user-chrome CSS file, e.g. if you want to change how tabs appear beyond just theming. though using a user-chrome CSS file is unfortunately a minor pain in the ass.)
I had to switch it to "multi-process mode" to get network requests from extensions to show up, but that broadly makes sense.
The process is roughly the same as inspecting the UI, you basically enable remote debugging and then launch the Browser Toolbox: https://superuser.com/questions/1608096/how-to-inspect-firef...
(this is also a great way to figure out what you need to do for a user-chrome CSS file, e.g. if you want to change how tabs appear beyond just theming. though using a user-chrome CSS file is unfortunately a minor pain in the ass.)
I had to switch it to "multi-process mode" to get network requests from extensions to show up, but that broadly makes sense.
e.g. here's ublock pulling a random block list that I clicked on to test: https://i.imgur.com/wBYbBM2.png
and here's Firefox itself updating the safe-browsing list in the background: https://i.imgur.com/JYxWwjW.png