The secret text didn't work for me.
I defined secret text in 'Manage Credentials'.
In the job configuration I checked the 'Use secret text(s) or file(s)',
added a variable base on the secret text I pre defined.
in the 'Logentries Forwarder' - I entered the $var - it didn't work
The 'Use secret text(s) or file(s)' appears after the 'Logentries Forwarder', maybe that is the reason it doesn't recognize the $var.