pacman update displays AUR gnome-shell-extension-blur-my-shell 30-1 as an update over the installed 28-2. However trying to install it asks for a provider of libmutter-10.0.so, all choices seem to be from the GNOME 42 release. Installation fails because of unresolvable dependencies.
For the time being the package can be kept at the current version or install it via the browser extension, that way the version compatible with your current version of the gnome-shell will be used: Blur my Shell - GNOME Shell Extensions This way you can keep using stable manjaro with the latest compatible version of the extension.
This is the way I use most of the extensions that are not in the manjaro repositories and minimize the use of the AUR.