@Omer Roth To get your NuGet package to appear in the Azure Site Extensions list, you need to create a feed that points to your NuGet package. You can then add this feed to the Site Extensions list in the Azure portal.
Here are the steps to create a feed and add it to the Site Extensions list:
- Create a NuGet package for your site extension and upload it to nuget.org.
- Create a new feed in Azure Artifacts or another NuGet feed provider.
- Add your NuGet package to the feed.
- In the Azure portal, go to your Web App or Function App and select "Extensions" from the menu.
- Click "Add" and select "Add from feed".
- Enter the URL of your NuGet feed and click "OK".
- Your site extension should now appear in the list of available extensions.
Regarding your second question, switching sites should not remove any installed extensions. The extensions are installed on a per-site basis, so they will only be removed if you uninstall them from the site..