A Variable Set - is a useful Octopus Deploy concept to share variable among multiple projects. Some prime candidate to live in Variable Sets are:

• Microservices settings referenced among multiple projects
• Database settings referenced among multiple projects
• Identity Manager settings
• In other words, some common settings shared among your enterprise should be extracted to their own variable sets and grouped logically.

In order to create a set go to Library->Variable Sets->Add New Variable Set:

Enter meaningful name and decent description:

Let's go ahead and enter Identity Server locations for your enterprise for different environments, like dev/stag/prod:

In the picture above we literally repeated the same variable for different variable names. This might happen when you change the legacy approach and introduce a new variable name for brand new projects. So to be backward compatible you have to duplicate all the settings. The good news is that we can introduce a new variable name and leverage old one settings. Consider it as an alias. In this case, we can skip duplications, defining the same environments, and the same values over and over: