hi,
from my understanding each action runs in its own session, so for example, if you run two command line actions after another, both would have their own session and so their own set of session parameters.
I don't know though how the "update environment variable" action works in CA-RA, not sure if it only does a session update or a "global" one (although a session one wouldn't really make sense). But I do know that running a command line with "setx" and the "/M" flag works, as I already did that.
an alternative would be, if we're strictly talking about the "run command line" action, that you define the session parameter in the inputs of the action (Environment Variable Names and Values)
hope this helps.
best regards
Michael