Hi,
The %APPL._ftfile is a builtin variable. It gets its value when the File Trigger has executed. The variable will get populated with full path and filename and is available to all jobs within the same application generation. Please note that each generation may have different value for this variable.
If you are just simulating an event, then it won't be able to show you the path or filename. If the variables value is dependent on job execution then it can't show that in simulation. The simulation can only show you what variables will get passed, how and when.
Thank you,
Nitin Pande
CA Technologies