That is not really how NixOS works – installing libraries globally is not supported: FAQ - NixOS Wiki
If you want to install GNOME Shell extension that depends on libraries or programs, you need to install it from Nixpkgs. Unfortunately, some manual work will likely still be required at the moment – although, we now should have most compatible extensions from the portal packaged, we still need gnomeExtensions: add patch framework and fix extensions by piegamesde · Pull Request #137131 · NixOS/nixpkgs · GitHub to allow patching the extensions without packaging them manually.