No need for a global library. Intellij IDEA supports adding libraries to your project directly from Maven. Here's how:
- Go to File -> Project Structure
- Select the Dependencies tab
- Click the + sign at the bottom to create a new library
- Choose "New Library" and seleect "From Maven" to add a new library from the public Maven repository
This brings up a search dialog which you can use to find the Maven dependency you want. Try searching for "org.scalatest:scalatest" to get the list of scalatest libraries.