There is no way to do that right now. 

Skybot does not inspect the SAP Job Definition for any potential variables at run time.

Also, the SAP Interface runs completely in java so there is no running of a script (.bat or .sh) in a command terminal at run time on the Agent which might have allowed for variables.

Note: SAP Variant changes & Event parameters do allow variables & are substituted on the server before sending to the Agent.