In Ignition 8.1, I need to prevent auto-logout on specific ProClient machines while maintaining 15-minute timeout for other users. The setSessionTimeout() function isn't available in this version
You'll need to dodge the project properties timeout, and switch to an expression-based solution.
You will need a way to identify the proclient machines based on IP address, username, role, or some other identifier.
Then take that info and write an expression to select a timeout value to compare with the lastActivity property.
How to add application timeout script in perspective? - Ignition - Inductive Automation Forum