In the image above, you can see that I had a field defined using two js expressions wrapped in {{...}} segments, separated by a pipe character padded by two whitespace characters. The expected result would be something like Mailer 1 Campaign | 1717096668103, but during execution the value would resolve to just the timestamp value from the second JS expression.
The fix was trivial - I just combined the expressions like so: {{startTrigger.data.campaign_name + ' | ' + moment.now().toString()}} and it now evaluates as expected. I'm guessing using multiple separate JS statements like this isn't a best practice, and in my case there wasn't any real reason to do so, but there also wasn't any clear indication that this syntax isn't supported, so I thought I'd share my findings here.
