I couldn't remember exactly what version of BP 6.x got the update where environment variable changes are indicated in the audit events log, so I checked the release notes. It turns out it wasn't added until 6.5.
Here's an excerpt from the Release Notes for BP 6.5:
"The following improvements have been made to Blue Prism auditing functionality:...
• Audit log entries are now created when environment variables are added, edited, and
deleted from the within the System tab."
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Dave Morris
3Ci @ Southern Company
Atlanta, GA
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Dave Morris, 3Ci at Southern Company