The Snaplex for this Pipeline is called Test. Because other Snaplexes might share the same environment name, you might want to rename the Environment.
In the SnapLogic Read Snap, set the Asset Type to Snaplex and specify the path.
In the Mapper Snap, you select the Input Schema element environment, and enter the expression to change the Environment name. Note that the Pass through option is selected.
In the Update Snap, you write the changes to the Snaplex and specify its file path.
When you go to the target folder in SnapLogic Manager, you can see that the Snaplex Environment name is changed.