I have created a 2010 list workflow using the following actions:
Find Manager of (Current Item: Reviewer 1) (output to (Variable: manager))
If (Variable: manager is (not empty)
Update item in (Current Item)
I published this workflow and went into my SP 2013 list workflow and did the following:
Start a List Workflow with (no parameters) on (Current Item)
Go to (End of Workflow)
Both workflows are set to start automatically with a new item.
I tested by adding a new item to the list. I can see that both workflows were successfully completed, but there is nothing that appears in the Manager column that I assigned the workflow to update.