I have an action list with a parameter, call it X. I call the action list, setting X to a value like: "%foo%\n %blah%", where \n is an actual new line/carriage return sequence.
Then, after saving, it looks like the full value is still stored in the Parameters property (if I access it via the Action Inspector), but if I edit the Action List list, the value now shows as "%foo%". And when I run it from fbcmd.exe it behaves as though the value was %foo% - though strangely in the IDE it still seems to use the full value.
Sorry I haven't tried to narrow it down more than that.
Also, weird stuff in general happens when you pass newline characters. At first you see the two control characters as normal, but when you attempt to edit that “value” field of the action list window, they disappear, and you see either what was before them or after them. It would be good if they’d show consistently as those characters.