The logic for gnome extensions is here:
Sorry Lyndeno. I give up. I tried for two hours.
- I just could not get the extension to update past version 40
- There is no way for me to debug the extension as could not find where it is installed, but I think even if I find it, I assume I cannot modify the extension to test or debug.
I think just for testing, better if you install extension like how it is installed in non nixos.
Option 1. Install Extension Manager app and use it to download and install extensions
https://search.nixos.org/packages?channel=23.11&show=gnome-extension-manager&from=0&size=50&sort=relevance&type=packages&query=gnome+shell+extension+manager
nix-env -iA nixos.gnome-extension-manager
Option 2. Install extension using commandline.
busctl --user call org.gnome.Shell.Extensions /org/gnome/Shell/Extensions org.gnome.Shell.Extensions InstallRemoteExtension s Battery-Health-Charging@maniacx.github.com
This will directly download extension from Gnome Extension website, install it and enable the extension. If you do not need you can uninstall from Extension app (which comes with Nixos).
Option 3. Install from Github, but you will have to also install gettext to able to run the installer.
Easiest and safest option is Option 2.