I really wanted something similar so I threw a quick and dirty tampermonkey script together to fetch the subscriptions from the settings page. I think it worked out pretty alright.
Thanks for sharing, but it doesn't seem to work for me. Even with my other scripts turned off. Looking at your screenshot, is that Safari on IOS? Maybe an OS specific issue as I'm on Windows using Firefox. Not pressuring you to fix it, just letting you know it might not work on other platforms.
No worries, it's my first published Tampermonkey script so there are probably a lot of quirks that should be ironed out.
I'm using Chrome on MacOS. Which extension are you using? I've only tested this in Tampermonkey and I did read somewhere that Greasemonkey may have dropped support for the GM_addStyle() function which I'm using.
If possible, it would really help if you could post any errors that you might be getting in the web inspector console.