Extension Manager is an app that allows you to install different shell extensions, to make your Linux experience better.
Extension Manager is a flatpak app on flathub repository, so installing Gnome Extension on your system could be done by using flatpak.
Extension Manager allows you also to manage the shell extensions that are currently installed on your system.
You can also remove any shell extension, If there's a shell extension that you don't want to use anymore, then you can simply delete it by using Gnome Extension.
In this tutorial, you will learn how to install Extension Manager on Debian 12, and also how to install shell extensions with Extensions manager.
Step 1 - Install Extension Manager
Extension Manager is uploaded on flathub repository. To install Extension Manager, simply run the command below
flatpak install flathub com.mattjakeman.ExtensionManager
Next, you need to confirm the installation of Extension Manager. Simply enter Y as answer on the confirmation prompt, and then press enter so that installing process begins

Once Extension Manager is installed, you should see the following output on your terminal .

Step 2 - Use Extension Manager
Now that Extension Manager is installed on your system, you are good to go and install Shell extensions that you like.
First, launch Extension Manager by running the command below
flatpak run com.mattjakeman.ExtensionManager

Once Extension manager is launched, you should see the main GUI window as shown in the image below

How to Install a shell extension
To install a shell extension is quite simple process. Go to "Browse" tab on Extension Manager, and search for the shell extension that you want to install

Next, simply click to the "Install" button to install the extension

Click to "Install" to confirm installing the extension

Installed extension will appear on Extension Manager window, on "Installed" tab under the "User-installed Extensions"

How to remove an extension
To remove a shell extension, go to "Installed" tab, then under "User-installed Extensions" you will see all installed extensions

Now To uninstall the extension, first locate the extension that you want to remove, next click to the down arrow icon of the extension

Next, simply click to "Remove" button to uninstall the extension

And confirm uninstalling by clicking "Yes" on the following prompt

Once extension has been uninstalled, it will also get removed from the "User-Installed Extensions" list.
How to disable an extension
In cases when you want to keep the extension but simply don't want to use it,then you can disable it.
To disable an extension, simply turn the extension switch off

Conclusion
By now you should know how to install Extension Manager on Debian 12. You should also know how to Manage extensions with Extension Manager.
It's worth mentioning that Extension Manager is a Gnome app, which means you can install it on any Linux distro that runs Gnome as desktop environment.